Electrochemical Fabrication Processes Incorporating Non-Platable Metals and/or Metals that are Difficult to Plate On

ABSTRACT

Embodiments are directed to electrochemically fabricating multi-layer three dimensional structures where each layer comprises at least one structural and at least one sacrificial material and wherein at least some metals or alloys are electrodeposited during the formation of some layers and at least some metals are deposited during the formation of some layers that are either difficult to electrodeposit and/or are difficult to electrodeposit onto. In some embodiments, the hard to electrodeposit metals (e.g. Ti, NiTi, W, Ta, Mo, etc.) may be deposited via chemical or physical vacuum deposition techniques while other techniques are used in other embodiments. In some embodiments, prior to electrodepositing metals, the surface of the previously formed layer is made to undergo appropriate preparation for receiving an electrodeposited material. Various surface preparation techniques are possible, including, for example, anodic activation, cathodic activation, and vacuum deposition of a seed layer and possibly an adhesion layer.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.11/478,934 (MF Docket No. P-US161-B-MF), filed Jun. 29, 2006. The '934application claims benefit of U.S. Provisional Patent Application No.60/695,328, filed Jun. 29, 2005 and the '934 application is also acontinuation in part of U.S. patent application Ser. Nos. 10/697,597(P-US082-A-MF), filed on Oct. 29, 2003; 10/841,100 (P-US093-A-MF), filedon May 7, 2004, now U.S. Pat. No. 7,109,118; Ser. No. 11/139,262(P-US144-A-MF), filed on May 26, 2005, now U.S. Pat. No. 7,501,328; Ser.No. 11/029,216 (P-US128-A-MF), filed on Jan. 3, 2005; Ser. No.10/841,300 (P-US099-A-MF), filed on May 7, 2004; and Ser. No. 10/607,931(P-US075-A-MG), filed Jun. 27, 2003, now U.S. Pat. No. 7,239,219. The'597 application claims benefit to U.S. Provisional Patent ApplicationNos. 60/422,008, filed Oct. 29, 2002; and 60/435,324, filed Dec. 20,2002. The '100 application claims benefit of U.S. Provisional PatentApplication Nos. 60/468,979, filed May 7, 2003; 60/469,053, filed May 7,2003; 60/533,891, filed Dec. 31, 2003; 60/468,977, filed May 7, 2003;and 60/534,204, filed Dec. 31, 2004. The '262 application claims benefitof U.S. Provisional Patent Application No. 60/574,733, filed May 26,2004 and the '262 application is a continuation in part of U.S. patentapplication Ser. No. 10/841,383 (P-US100-A-MF), filed May 7, 2004, nowU.S. Pat. No. 7,195,989. The '383 application claims benefit of U.S.Provisional Patent Application Nos. 60/468,979, filed May 7, 2003;60/469,053, filed May 7, 2003; and 60/533,891, filed Dec. 31, 2003. The'216 application claims benefit of U.S. Provisional Patent ApplicationNos. 60/533,932, filed Dec. 31, 2003; 60/534,157, filed Dec. 31, 2003;60/533,891, filed Dec. 31, 2003; and 60/574,733, filed May 26, 2004.Each of these applications in incorporated herein by reference as if setfourth in full.

FIELD OF THE INVENTION

The present invention relates generally to the field ofelectrochemically fabricating multi-layer three dimensional (e.g.micro-scale or meso-scale) structures, parts, components, or deviceswhere each layer is formed from a plurality of deposited materials andwherein at least one of the materials is a non-electroplatable metal oris a metal that is difficult to electroplate directly on.

BACKGROUND OF THE INVENTION

A technique for forming three-dimensional structures (e.g. parts,components, devices, and the like) from a plurality of adhered layerswas invented by Adam L. Cohen and is known as ElectrochemicalFabrication. It is being commercially pursued by Microfabrica Inc. ofVan Nuys, Calif. under the name EFAB™. This technique was described inU.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This electrochemicaldeposition technique allows the selective deposition of a material usinga unique masking technique that involves the use of a mask that includespatterned conformable material on a support structure that isindependent of the substrate onto which plating will occur. Whendesiring to perform an electrodeposition using the mask, the conformableportion of the mask is brought into contact with a substrate while inthe presence of a plating solution such that the contact of theconformable portion of the mask to the substrate inhibits deposition atselected locations. For convenience, these masks might be genericallycalled conformable contact masks; the masking technique may begenerically called a conformable contact mask plating process. Morespecifically, in the terminology of Microfabrica Inc. of Van Nuys,Calif. such masks have come to be known as INSTANT MASKS™ and theprocess known as INSTANT MASKING™ or INSTANT MASK™ plating. Selectivedepositions using conformable contact mask plating may be used to formsingle layers of material or may be used to form multi-layer structures.The teachings of the '630 patent are hereby incorporated herein byreference as if set forth in full herein. Since the filing of the patentapplication that led to the above noted patent, various papers aboutconformable contact mask plating (i.e. INSTANT MASKING) andelectrochemical fabrication have been published:

-   -   (1) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Batch production of functional, fully-dense metal        parts with micro-scale features”, Proc. 9th Solid Freeform        Fabrication, The University of Texas at Austin, p161, August        1998.    -   (2) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High        Aspect Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro        Mechanical Systems Workshop, IEEE, p244, January 1999.    -   (3) A. Cohen, “3-D Micromachining by Electrochemical        Fabrication”, Micromachine Devices, March 1999.    -   (4) G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P.        Will, “EFAB: Rapid Desktop Manufacturing of True 3-D        Microstructures”, Proc. 2nd International Conference on        Integrated MicroNanotechnology for Space Applications, The        Aerospace Co., April 1999.    -   (5) F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, 3rd        International Workshop on High Aspect Ratio MicroStructure        Technology (HARMST'99), June 1999.    -   (6) A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P.        Will, “EFAB: Low-Cost, Automated Electrochemical Batch        Fabrication of Arbitrary 3-D Microstructures”, Micromachining        and Microfabrication Process Technology, SPIE 1999 Symposium on        Micromachining and Microfabrication, September 1999.    -   (7) F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, MEMS        Symposium, ASME 1999 International Mechanical Engineering        Congress and Exposition, November, 1999.    -   (8) A. Cohen, “Electrochemical Fabrication (EFAB™)”, Chapter 19        of The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC Press,        2002.    -   (9) Microfabrication—Rapid Prototyping's Killer Application”,        pages 1-5 of the Rapid Prototyping Report, CAD/CAM Publishing,        Inc., June 1999.

The disclosures of these nine publications are hereby incorporatedherein by reference as if set forth in full herein.

The electrochemical deposition process may be carried out in a number ofdifferent ways as set forth in the above patent and publications. In oneform, this process involves the execution of three separate operationsduring the formation of each layer of the structure that is to beformed:

-   -   1. Selectively depositing at least one material by        electrodeposition upon one or more desired regions of a        substrate.    -   2. Then, blanket depositing at least one additional material by        electrodeposition so that the additional deposit covers both the        regions that were previously selectively deposited onto, and the        regions of the substrate that did not receive any previously        applied selective depositions.    -   3. Finally, planarizing the materials deposited during the first        and second operations to produce a smoothed surface of a first        layer of desired thickness having at least one region containing        the at least one material and at least one region containing at        least the one additional material.

After formation of the first layer, one or more additional layers may beformed adjacent to the immediately preceding layer and adhered to thesmoothed surface of that preceding layer. These additional layers areformed by repeating the first through third operations one or more timeswherein the formation of each subsequent layer treats the previouslyformed layers and the initial substrate as a new and thickeningsubstrate.

Once the formation of all layers has been completed, at least a portionof at least one of the materials deposited is generally removed by anetching process to expose or release the three-dimensional structurethat was intended to be formed.

The preferred method of performing the selective electrodepositioninvolved in the first operation is by conformable contact mask plating.In this type of plating, one or more conformable contact (CC) masks arefirst formed. The CC masks include a support structure onto which apatterned conformable dielectric material is adhered or formed. Theconformable material for each mask is shaped in accordance with aparticular cross-section of material to be plated. At least one CC maskis needed for each unique cross-sectional pattern that is to be plated.

The support for a CC mask is typically a plate-like structure formed ofa metal that is to be selectively electroplated and from which materialto be plated will be dissolved. In this typical approach, the supportwill act as an anode in an electroplating process. In an alternativeapproach, the support may instead be a porous or otherwise perforatedmaterial through which deposition material will pass during anelectroplating operation on its way from a distal anode to a depositionsurface. In either approach, it is possible for CC masks to share acommon support, i.e. the patterns of conformable dielectric material forplating multiple layers of material may be located in different areas ofa single support structure. When a single support structure containsmultiple plating patterns, the entire structure is referred to as the CCmask while the individual plating masks may be referred to as“submasks”. In the present application such a distinction will be madeonly when relevant to a specific point being made.

In preparation for performing the selective deposition of the firstoperation, the conformable portion of the CC mask is placed inregistration with and pressed against a selected portion of thesubstrate (or onto a previously formed layer or onto a previouslydeposited portion of a layer) on which deposition is to occur. Thepressing together of the CC mask and substrate occur in such a way thatall openings, in the conformable portions of the CC mask contain platingsolution. The conformable material of the CC mask that contacts thesubstrate acts as a barrier to electrodeposition while the openings inthe CC mask that are filled with electroplating solution act as pathwaysfor transferring material from an anode (e.g. the CC mask support) tothe non-contacted portions of the substrate (which act as a cathodeduring the plating operation) when an appropriate potential and/orcurrent are supplied.

An example of a CC mask and CC mask plating are shown in FIGS. 1A-1C.FIG. 1A shows a side view of a CC mask 8 consisting of a conformable ordeformable (e.g. elastomeric) insulator 10 patterned on an anode 12. Theanode has two functions. One is as a supporting material for thepatterned insulator 10 to maintain its integrity and alignment since thepattern may be topologically complex (e.g., involving isolated “islands”of insulator material). The other function is as an anode for theelectroplating operation. FIG. 1A also depicts a substrate 6 separatedfrom mask 8. CC mask plating selectively deposits material 22 onto asubstrate 6 by simply pressing the insulator against the substrate thenelectrodepositing material through apertures 26 a and 26 b in theinsulator as shown in FIG. 1B. After deposition, the CC mask isseparated, preferably non-destructively, from the substrate 6 as shownin FIG. 1C. The CC mask plating process is distinct from a“through-mask” plating process in that in a through-mask plating processthe separation of the masking material from the substrate would occurdestructively. As with through-mask plating, CC mask plating depositsmaterial selectively and simultaneously over the entire layer. Theplated region may consist of one or more isolated plating regions wherethese isolated plating regions may belong to a single structure that isbeing formed or may belong to multiple structures that are being formedsimultaneously. In CC mask plating as individual masks are notintentionally destroyed in the removal process, they may be usable inmultiple plating operations.

Another example of a CC mask and CC mask plating is shown in FIGS.1D-1G. FIG. 1D shows an anode 12′ separated from a mask 8′ that includesa patterned conformable material 10′ and a support structure 20. FIG. 1Dalso depicts substrate 6 separated from the mask 8′. FIG. 1E illustratesthe mask 8′ being brought into contact with the substrate 6. FIG. 1Fillustrates the deposit 22′ that results from conducting a current fromthe anode 12′ to the substrate 6. FIG. 1G illustrates the deposit 22′ onsubstrate 6 after separation from mask 8′. In this example, anappropriate electrolyte is located between the substrate 6 and the anode12′ and a current of ions coming from one or both of the solution andthe anode are conducted through the opening in the mask to the substratewhere material is deposited. This type of mask may be referred to as ananodeless INSTANT MASK™ (AIM) or as an anodeless conformable contact(ACC) mask.

Unlike through-mask plating, CC mask plating allows CC masks to beformed completely separate from the fabrication of the substrate onwhich plating is to occur (e.g. separate from a three-dimensional (3D)structure that is being formed). CC masks may be formed in a variety ofways, for example, a photolithographic process may be used. All maskscan be generated simultaneously, e.g. prior to structure fabricationrather than during it. This separation makes possible a simple,low-cost, automated, self-contained, and internally-clean “desktopfactory” that can be installed almost anywhere to fabricate 3Dstructures, leaving any required clean room processes, such asphotolithography to be performed by service bureaus or the like.

An example of the electrochemical fabrication process discussed above isillustrated in FIGS. 2A-2F. These figures show that the process involvesdeposition of a first material 2 which is a sacrificial material and asecond material 4 which is a structural material. The CC mask 8, in thisexample, includes a patterned conformable material (e.g. an elastomericdielectric material) 10 and a support 12 which is made from depositionmaterial 2. The conformal portion of the CC mask is pressed againstsubstrate 6 with a plating solution 14 located within the openings 16 inthe conformable material 10. An electric current, from power supply 18,is then passed through the plating solution 14 via (a) support 12 whichdoubles as an anode and (b) substrate 6 which doubles as a cathode. FIG.2A illustrates that the passing of current causes material 2 within theplating solution and material 2 from the anode 12 to be selectivelytransferred to and plated on the substrate 6. After electroplating thefirst deposition material 2 onto the substrate 6 using CC mask 8, the CCmask 8 is removed as shown in FIG. 2B. FIG. 2C depicts the seconddeposition material 4 as having been blanket-deposited (i.e.non-selectively deposited) over the previously deposited firstdeposition material 2 as well as over the other portions of thesubstrate 6. The blanket deposition occurs by electroplating from ananode (not shown), composed of the second material, through anappropriate plating solution (not shown), and to the cathode/substrate6. The entire two-material layer is then planarized to achieve precisethickness and flatness as shown in FIG. 2D. After repetition of thisprocess for all layers, the multi-layer structure 20 formed of thesecond material 4 (i.e. structural material) is embedded in firstmaterial 2 (i.e. sacrificial material) as shown in FIG. 2E. The embeddedstructure is etched to yield the desired device, i.e. structure 20, asshown in FIG. 2F.

Various components of an exemplary manual electrochemical fabricationsystem 32 are shown in FIGS. 3A-3C. The system 32 consists of severalsubsystems 34, 36, 38, and 40. The substrate holding subsystem 34 isdepicted in the upper portions of each of FIGS. 3A-3C and includesseveral components: (1) a carrier 48, (2) a metal substrate 6 onto whichthe layers are deposited, and (3) a linear slide 42 capable of movingthe substrate 6 up and down relative to the carrier 48 in response todrive force from actuator 44. Subsystem 34 also includes an indicator 46for measuring differences in vertical position of the substrate whichmay be used in setting or determining layer thicknesses and/ordeposition thicknesses. The subsystem 34 further includes feet 68 forcarrier 48 which can be precisely mounted on subsystem 36.

The CC mask subsystem 36 shown in the lower portion of FIG. 3A includesseveral components: (1) a CC mask 8 that is actually made up of a numberof CC masks (i.e. submasks) that share a common support/anode 12, (2)precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 on whichthe feet 68 of subsystem 34 can mount, and (5) a tank 58 for containingthe electrolyte 16. Subsystems 34 and 36 also include appropriateelectrical connections (not shown) for connecting to an appropriatepower source (not shown) for driving the CC masking process.

The blanket deposition subsystem 38 is shown in the lower portion ofFIG. 3B and includes several components: (1) an anode 62, (2) anelectrolyte tank 64 for holding plating solution 66, and (3) frame 74 onwhich feet 68 of subsystem 34 may sit. Subsystem 38 also includesappropriate electrical connections (not shown) for connecting the anodeto an appropriate power supply (not shown) for driving the blanketdeposition process.

The planarization subsystem 40 is shown in the lower portion of FIG. 3Cand includes a lapping plate 52 and associated motion and controlsystems (not shown) for planarizing the depositions.

In addition to teaching the use of CC masks for electrodepositionpurposes, the '630 patent also teaches that the CC masks may be placedagainst a substrate with the polarity of the voltage reversed andmaterial may thereby be selectively removed from the substrate. Itindicates that such removal processes can be used to selectively etch,engrave, and polish a substrate, e.g., a plaque.

The '630 patent further indicates that the electroplating methods andarticles disclosed therein allow fabrication of devices from thin layersof materials such as, e.g., metals, polymers, ceramics, andsemiconductor materials. It further indicates that although theelectroplating embodiments described therein have been described withrespect to the use of two metals, a variety of materials, e.g.,polymers, ceramics and semiconductor materials, and any number of metalscan be deposited either by the electroplating methods therein, or inseparate processes that occur throughout the electroplating method. Itindicates that a thin plating base can be deposited, e.g., bysputtering, over a deposit that is insufficiently conductive (e.g., aninsulating layer) so as to enable subsequent electroplating. It alsoindicates that multiple support materials (i.e. sacrificial materials)can be included in the electroplated element allowing selective removalof the support materials.

The '630 patent additionally teaches that the electroplating methodsdisclosed therein can be used to manufacture elements having complexmicrostructure and close tolerances between parts. An example is givenwith the aid of FIGS. 14A-14E of that patent. In the example, elementshaving parts that fit with close tolerances, e.g., having gaps betweenabout 1-5 um, including electroplating the parts of the device in anunassembled, preferably pre-aligned, state and once fabricated. In suchembodiments, the individual parts can be moved into operational relationwith each other or they can simply fall together. Once together theseparate parts may be retained by clips or the like.

Another method for forming microstructures from electroplated metals(i.e. using electrochemical fabrication techniques) is taught in U.S.Pat. No. 5,190,637 to Henry Guckel, entitled “Formation ofMicrostructures by Multiple Level Deep X-ray Lithography withSacrificial Metal layers”. This patent teaches the formation of metalstructure utilizing mask exposures. A first layer of a primary metal iselectroplated onto an exposed plating base to fill a void in aphotoresist, the photoresist is then removed and a secondary metal iselectroplated over the first layer and over the plating base. Theexposed surface of the secondary metal is then machined down to a heightwhich exposes the first metal to produce a flat uniform surfaceextending across the both the primary and secondary metals. Formation ofa second layer may then begin by applying a photoresist layer over thefirst layer and then repeating the process used to produce the firstlayer. The process is then repeated until the entire structure is formedand the secondary metal is removed by etching. The photoresist is formedover the plating base or previous layer by casting and the voids in thephotoresist are formed by exposure of the photoresist through apatterned mask via X-rays or UV radiation.

The '637 patent teaches the locating of a plating base onto a substratein preparation for electroplating materials onto the substrate. Theplating base is indicated as typically involving the use of a sputteredfilm of an adhesive metal, such as chromium or titanium, and then asputtered film of the metal that is to be plated. It is also taught thatthe plating base may be applied over an initial sacrificial layer ofmaterial on the substrate so that the structure and substrate may bedetached if desired. In such cases after formation of the structure theplating base may be patterned and removed from around the structure andthen the sacrificial layer under the plating base may be dissolved tofree the structure. Substrate materials mentioned in the '637 patentinclude silicon, glass, metals, and silicon with protected processedsemiconductor devices. A specific example of a plating base includesabout 150 angstroms of titanium and about 300 angstroms of nickel, bothof which are sputtered at a temperature of 160° C. In another example itis indicated that the plating base may consist of 150 angstroms oftitanium and 150 angstroms of nickel where both are applied bysputtering.

Electrochemical Fabrication provides the ability to form prototypes andcommercial quantities of miniature objects, parts, structures, devices,and the like at reasonable costs and in reasonable times. In fact,Electrochemical Fabrication is an enabler for the formation of manystructures that were hitherto impossible to produce. ElectrochemicalFabrication opens the spectrum for new designs and products in manyindustrial fields. Even though Electrochemical Fabrication offers thisnew capability and it is understood that Electrochemical Fabricationtechniques can be combined with designs and structures known withinvarious fields to produce new structures, certain uses forElectrochemical Fabrication provide designs, structures, capabilitiesand/or features not known or obvious in view of the state of the art.

A need exists in various fields for miniature devices having improvedcharacteristics, reduced fabrication times, reduced fabrication costs,simplified fabrication processes, greater versatility in device design,improved selection of materials, improved material properties, more costeffective and less risky production of such devices, and/or moreindependence between geometric configuration and the selectedfabrication process.

SUMMARY OF THE INVENTION

It is an object of some aspects of the invention to provide an improvedmethod for forming multi-layer three-dimensional structures where astructural material included on one or more layers is a metal thatcannot be readily (e.g. in a commercially reasonable manner)electroplated or on which it is difficult to electroplate other metals

It is an object of some aspects of the invention to provide an improvedmethod for forming multi-layer three-dimensional structures where ashape memory alloy (e.g. nickel titanium, NiTi) is included on one ormore layers as a structural material

Other objects and advantages of various aspects and embodiments of theinvention will be apparent to those of skill in the art upon review ofthe teachings herein. The various aspects of the invention, set forthexplicitly herein or otherwise ascertained from the teachings herein,may address one or more of the above objects alone or in combination, oralternatively may address some other object ascertained from theteachings herein. It is not necessarily intended that all objects beaddressed by any single aspect of the invention even though that may bethe case with regard to some aspects.

A first aspect of the invention provides an improved method of forming amulti-layer three-dimensional structure, including: (A) forming aplurality of successive layers of the structure with each successivelayer, except for a first layer, adhered to a previously formed layerand with each successive layer comprising at least two materials, one ofwhich is a structural material and the other of which is a sacrificialmaterial, and wherein each successive layer defines a successivecross-section of the three-dimensional structure, and wherein theforming of each of the plurality of successive layers includes: (i)depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; and (B) after the forming of theplurality of successive layers, separating at least a portion of thesacrificial material from the structural material to reveal thethree-dimensional structure, wherein the improvement includes:depositing the first material via an electrodeposition process duringformation of a given layer; depositing the second material via anon-electrodeposition process during formation of a given layer; whereinthe first material is a metal and wherein the second material is an HDETmetal, and wherein the first material is the sacrificial material andthe second material is the structural material.

A second aspect of the invention provides an improved method of forminga multi-layer three-dimensional structure, including: (A) forming aplurality of successive layers of the structure with each successivelayer, except for a first layer, adhered to a previously formed layerand with each successive layer comprising at least two materials, one ofwhich is a structural material and the other of which is a sacrificialmaterial, and wherein each successive layer defines a successivecross-section of the three-dimensional structure, and wherein theforming of each of the plurality of successive layers includes: (i)depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; and (B) after the forming of theplurality of successive layers, separating at least a portion of thesacrificial material from the structural material to reveal thethree-dimensional structure, wherein the improvement includes:depositing the first material via a non-electrodeposition process duringformation of a given layer; depositing the second material via anelectrodeposition process during formation of the given layer; whereinthe first material is an HDET metal and wherein the second material is ametal, and wherein the first material is the structural material and thesecond material sacrificial material.

A third aspect of the invention provides an improved method of forming amulti-layer three-dimensional structure, including: (A) forming aplurality of successive layers of the structure with each successivelayer, except for a first layer, adhered to a previously formed layerand with each successive layer comprising at least three materials, oneof which is a structural material and the other of which is asacrificial material, and wherein each successive layer defines asuccessive cross-section of the three-dimensional structure, and whereinthe forming of each of the plurality of successive layers includes: (i)depositing a first of the at least two materials; (ii) depositing asecond of the at least two materials; and (B) after the forming of theplurality of successive layers, separating at least a portion of thesacrificial material from the structural material to reveal thethree-dimensional structure, wherein the improvement includes:depositing a first material structural or sacrificial material duringformation of a given layer; depositing a second structural orsacrificial material during formation of the given layer, depositing athird structural or sacrificial material during formation of the givenlayer; wherein at least one of the first-third materials is asacrificial material, at least one of the first-third materials is astructural material, at least two of the first-third materials aremetals, and least one of the metals is electrodeposited, and at leastone structural material is an HDET metal

Other aspects of the invention will be understood by those of skill inthe art upon review of the teachings herein. Other aspects of theinvention may involve combinations of the above noted aspects of theinvention. Other aspects of the invention may involve apparatus that canbe used in implementing one or more of the above method aspects of theinvention. These other aspects of the invention may provide variouscombinations of the aspects presented above as well as provide otherconfigurations, structures, functional relationships, and processes thathave not been specifically set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C schematically depict side views of various stages of a CCmask plating process, while FIGS. 1D-G schematically depict a side viewsof various stages of a CC mask plating process using a different type ofCC mask.

FIGS. 2A-2F schematically depict side views of various stages of anelectrochemical fabrication process as applied to the formation of aparticular structure where a sacrificial material is selectivelydeposited while a structural material is blanket deposited.

FIGS. 3A-3C schematically depict side views of various examplesubassemblies that may be used in manually implementing theelectrochemical fabrication method depicted in FIGS. 2A-2F.

FIGS. 4A-4F schematically depict the formation of a first layer of astructure using adhered mask plating where the blanket deposition of asecond material overlays both the openings between deposition locationsof a first material and the first material itself

FIG. 4G depicts the completion of formation of the first layer resultingfrom planarizing the deposited materials to a desired level.

FIGS. 4H and 4I respectively depict the state of the process afterformation of the multiple layers of the structure and after release ofthe structure from the sacrificial material.

FIG. 5 provides a block diagram of the major steps in a processaccording to a first group of embodiments where a first structural orsacrificial material is electrolytically deposited and a secondstructural or sacrificial material is an HTED metal or alloy and is thusnon-electrolytically deposited.

FIG. 6A provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is an HTED metal or alloy and thus isnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is selectively deposited.

FIG. 6B provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is an HTED metal or alloy and is thusnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is blanket deposited to cover and fill voids in a maskingmaterial.

FIG. 6C provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is and HTED metal or alloy and is thusnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is blanket deposited and is then patterned to form voidsinto which the second material can be deposited.

FIG. 7A provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6A with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

FIG. 7B provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6B with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

FIG. 7C provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6C with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

FIG. 8 provides a block diagram of the major steps (along with variousalternatives) in a process according to a fourth group of embodimentswhere the number of materials deposited per layer is variable.

FIGS. 9A-9F depict schematic side views of various states of a firstspecific embodiment of the first group of embodiments as applied to anexample structure, where the second material is an HTED metal or alloyand is thus deposited in a non-electrolytic manner.

FIGS. 10A-10F depict schematic side views of various states of a moredetailed example of the first specific embodiment of the second group ofembodiments and in particular of the process of FIG. 6B as applied to anexample structure, where the first material is an HTED metal or alloyand is thus a patterned via non-electrolytic deposition.

FIGS. 11A-11H depict schematic side views of various states of a secondspecific embodiment of the first group of embodiments where the secondmaterial is an HTED metal or alloy and is thus deposited in anon-electrolytic, flowable form (e.g., a liquid, a paste, or a powdernor requiring consolidation).

FIGS. 12A-12H depict schematic side views of various states of a thirdspecific embodiment of the first group of embodiments where the firstmaterial is deposited electrolytically and the second material is anHTED metal or alloy and is deposited in a powder form that requiresconsolidation.

FIGS. 13A-13H depict schematic side views of various states of a fourthspecific embodiment of the first group of embodiments as applied to aspecific example structure where the second material is an HTED metal oralloy and is deposited in sheet form, then deformed mechanically,sonically, and/or thermally.

FIGS. 14A-14N depict various states of a process for forming athree-dimensional structure according to a fifth specific embodiment ofthe first group of embodiments of the invention in which multilayerstructures of nickel titanium (NiTi), tantalum (Ta), or titanium (Ti) orother material (HTED metal) that is difficult to plate onto can befabricated.

FIGS. 15A-15H depict various states of a process for forming athree-dimensional structure according to a sixth specific embodiment ofthe first group of embodiments of the invention in which a coating ofthe sacrificial material to be electrodeposited over a previously formedlayer that contains or may contain a structural material that is hard toelectroplate over (i.e. an HTED metal, e.g. NiTi) is first applied usingvacuum processing and then increased in height via electroplating.

FIGS. 16A-16I depict various states of a process for forming athree-dimensional structure according to a seventh specific embodimentof the first group of embodiments of the invention in which a coating ofthe sacrificial material, to be electrodeposited, over a previouslyformed layer that contains or may contain a structural material that ishard to electroplate over (i.e. an HTED metal, e.g. NiTi) is firstapplied to selected portions of a previously formed layer via voids in amasking material and prior to thickening the coating of the firstmaterial, a lift off process is used to remove the vacuum depositedmaterial from above the masking material.

FIGS. 17A-17J depict various states of a process for forming athree-dimensional structure according to an eighth specific embodimentof the first group of embodiments of the invention in which a coating ofthe sacrificial material, to be electrodeposited, over a previouslyformed layer that contains or may contain a structural material that ishard to electroplate over (i.e. an HTED metal, e.g. NiTi) is firstapplied over the entire previous layer via a blanket vacuum depositionafter which masking material is applied and the material patterned viaetching.

FIGS. 18A-18C provide various views of a sputtering fixture andcomponents thereof that allow controlled sputtering on a surface of awafer.

FIGS. 19A-19D illustrate an example device that self-assembles as aresult of undergoing temperature changes. FIGS. 21A-21D depict, incross-section, an arrangement/process which allows wafer-scaleelectropolishing of a fabricated device located on a substrate.

FIG. 20 provides an example of a typical bimorph device with a high CTEmaterial on the top and a relatively low CTE material on the bottom.

FIG. 21 provides another example of a bimorph in which the top materialis a high CTE material and the bottom material is a shape memorymaterial.

FIGS. 23A-23E illustrate an embodiment where mandrels for shape-settingare co-fabricated along with devices.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of one form ofelectrochemical fabrication that are known. Other electrochemicalfabrication techniques are set forth in the '630 patent referencedabove, in the various previously incorporated publications, in variousother patents and patent applications incorporated herein by reference,still others may be derived from combinations of various approachesdescribed in these publications, patents, and applications, or areotherwise known or ascertainable by those of skill in the art from theteachings set forth herein. All of these techniques may be combined withthose of the various embodiments of various aspects of the invention toyield enhanced embodiments. Still other embodiments may be derived fromcombinations of the various embodiments explicitly set forth herein.

FIGS. 4A-4I illustrate various stages in the formation of a single layerof a multi-layer fabrication process where a second metal is depositedon a first metal as well as in openings in the first metal so that thefirst and second metal form part of the layer. In FIG. 4A a side view ofa substrate 82 is shown, onto which patternable photoresist 84 is castas shown in FIG. 4B. In FIG. 4C, a pattern of resist is shown thatresults from the curing, exposing, and developing of the resist. Thepatterning of the photoresist 84 results in openings or apertures92(a)-92(c) extending from a surface 86 of the photoresist through thethickness of the photoresist to surface 88 of the substrate 82. In FIG.4D a metal 94 (e.g. nickel) is shown as having been electroplated intothe openings 92(a)-92(c). In FIG. 4E the photoresist has been removed(i.e. chemically stripped) from the substrate to expose regions of thesubstrate 82 which are not covered with the first metal 94. In FIG. 4F asecond metal 96 (e.g. silver) is shown as having been blanketelectroplated over the entire exposed portions of the substrate 82(which is conductive) and over the first metal 94 (which is alsoconductive). FIG. 4G depicts the completed first layer of the structurewhich has resulted from the planarization of the first and second metalsdown to a height that exposes the first metal and sets a thickness forthe first layer. In FIG. 4H the result of repeating the process stepsshown in FIGS. 4B-4 G several times to form a multi-layer structure areshown where each layer consists of two materials. For most applications,one of these materials is removed as shown in FIG. 4I to yield a desired3-D structure 98 (e.g. component or device).

Various embodiments of various aspects of the invention are directed toformation of three-dimensional structures from materials some of whichmay be electrodeposited or electroless deposited. Some of thesestructures may be formed from a single layer of one or more depositedmaterial while others are formed from a plurality of layers eachincluding at least two materials (e.g. 2 or more layers, more preferablyfive or more layers, and most preferably ten or more layers). In someembodiments structures having features positioned with micron levelprecision and minimum features size on the order of tens of microns areto be formed. In other embodiments structures with less precise featureplacement and/or larger minimum features may be formed. In still otherembodiments, higher precision and smaller minimum feature sizes may bedesirable.

The various embodiments, alternatives, and techniques disclosed hereinmay form multi-layer structures using a single patterning technique onall layers or using different patterning techniques on different layers.For example, Various embodiments of the invention may perform selectivepatterning operations using conformable contact masks and maskingoperations (i.e. operations that use masks which are contacted to butnot adhered to a substrate), proximity masks and masking operations(i.e. operations that use masks that at least partially selectivelyshield a substrate by their proximity to the substrate even if contactis not made), non-conformable masks and masking operations (i.e. masksand operations based on masks whose contact surfaces are notsignificantly conformable), and/or adhered masks and masking operations(masks and operations that use masks that are adhered to a substrateonto which selective deposition or etching is to occur as opposed toonly being contacted to it). Adhered mask may be formed in a number ofways including (1) by application of a photoresist, selective exposureof the photoresist, and then development of the photoresist, (2)selective transfer of pre-patterned masking material, and/or (3) directformation of masks from computer controlled depositions of material.

Patterning operations may be used in selectively depositing materialand/or may be used in the selective etching of material. Selectivelyetched regions may be selectively filled in or filled in via blanketdeposition, or the like, with a different desired material. In someembodiments, the layer-by-layer build up may involve the simultaneousformation of portions of multiple layers. In some embodiments,depositions made in association with some layer levels may result indepositions to regions associated with other layer levels. Such use ofselective etching and interlaced material deposited in association withmultiple layers is described in U.S. patent application Ser. No.10/434,519, by Smalley, and entitled “Methods of and Apparatus forElectrochemically Fabricating Structures Via Interlaced Layers or ViaSelective Etching and Filling of Voids layer elements” which is herebyincorporated herein by reference as if set forth in full.

In the present application the following terms are generally intended tohave the following definitions though the meaning of particular terms asused in particular contexts may vary from these definitions if thecontext makes it clear what the term is intended to mean in thatcircumstance.

The terms “three-dimensional structure”, “structure”, “part”,“component”, “device”, and the like shall refer generally to intended oractually fabricated three-dimensional configurations (e.g. of structuralmaterial) that are intended to be used for a particular purpose. Suchstructures, etc. may, for example, be designed with the aid of athree-dimensional CAD system. In some embodiments, such structures maybe formable from a single layer of structural material while in mostembodiments, such structures will be formable from a plurality ofadhered layers. When designing such structures, for example, theformation process that will be used in fabricating the structure may ormay not be taken into consideration. For example, if the structure is tobe formed from a plurality of adhered layers, it may be desirable totake into consideration the vertical levels that define layertransitions so that structural features are precisely located at layerboundary levels. The structures may be designed with sloping sidewallsor with vertical sidewalls. In designing such a three-dimensionalstructures they may be designed in a positive manner (i.e. features ofthe structure itself defined) or in a negative manner (i.e. regions orfeatures of sacrificial material within a build volume defined), or as acombination of both.

The terms “build axis” or “build orientation” refer to a direction thatis generally perpendicular to the planes of layers from which athree-dimensional structure is formed and it points in the directionfrom previously formed layers to successively formed layers. The buildorientation will generally be considered to extend in the verticaldirection regardless of the actual orientation, with respect to gravity,of the build axis during layer formation (e.g. regardless of whether thedirection of layer stacking is horizontal relative to the earth'sgravity, upside down relative to gravity, or at some other anglerelative to the earth's gravity).

The term “structural material” shall generally refer to one or moreparticular materials that are deposited during formation of one or morebuild layers at particular lateral positions, where the material isgenerally intended to form part or all of a final three-dimensionalstructure and where thicknesses of the particular material associatedwith one or more particular layers is typically substantially that ofthe thickness of that layer or the thicknesses of those layers. Duringformation of particular layers, structural material thickness may varyfrom the layer thicknesses by generally relative thin adhesion layerthicknesses, seed layer thicknesses, barrier layer thicknesses, or thelike, or at edges of features where sloping sidewalls may exist. In someembodiments, the structural material associated with particular layersmay be formed from a plurality of distinctly deposited material whosecombination defines an effective structural material.

The term “sacrificial material” shall generally refer to one or moreparticular materials that are deposited during formation of one or morebuild layers at particular lateral positions, where the material isgenerally intended to be removed from a final three-dimensionalstructure prior to putting it to its intended use. Sacrificial materialdoes not generally refer to masking materials, or the like, that areapplied during formation of a particular layer and then removed prior tocompletion of formation of that layer. Sacrificial material generallyforms a portion of a plurality of build layers and is separated fromstructural material after formation of a plurality of layers (e.g. aftercompletion of formation of all build layers). Some portion of asacrificial material may become a pseudo structural material if it iscompletely encapsulated or effectively trapped by structural materialsuch that it is not removed prior to putting the structure to use. Forexample, a copper sacrificial material may be intentionally encapsulatedby a structural material (e.g. nickel or a nickel alloy) so as toimprove thermal conductive or electrical conductive of the structure asa whole. The thicknesses of a particular sacrificial material associatedwith one or more particular layers is typically substantially that ofthe thickness of that layer or the thicknesses of those layers. Duringformation of particular layers, sacrificial material thickness may varyfrom the layer thicknesses by generally relative thin adhesion materialthicknesses, seed material thicknesses, barrier material thicknesses, orthe like, or at edges of features where sloping sidewalls may exist. Insome embodiments, the sacrificial material associated with particularlayers may be formed from a plurality of distinctly deposited materialwhose combination defines an effective structural material.

The term “build layer”, “structural layer”, or simply “layer” generallyrefers to materials deposited within a build volume located between twoplanes spaced by a “layer thickness” along the build axis where at leastone structural material exists in one or more lateral positions and atleast one sacrificial material exists in one or more other lateralpositions. During fabrication, build layers are generally stacked oneupon another but in some embodiments, it is possible that build layerswill be separated one from another, in whole or in part, by relativethin coatings of adhesion layer material, seed layer material, barrierlayer material, or the like.

The term “layer thickness” is the height along the build axis between alower boundary of a build layer and an upper boundary of that buildlayer. Layer thicknesses, for example may be in the two micron to fiftymicron range, with ten micron to 30 micron being common. In someembodiments layer thicknesses may be thinner than 2 microns or thickerthan fifty microns. In many embodiments, deposition thickness (i.e. thethickness of any particular material after it is deposited) is generallygreater than the layer thickness and a net deposit thickness is set viaone or more planarization processes which may include, for example,mechanical abrasion (e.g. lapping, fly cutting, polishing, and the like)and/or chemical etching (e.g. using selective or non-selectiveetchants). The lower boundary and upper boundary for a build layer maybe set and defined in different ways. From a design point of view theymay be set based on a desired vertical resolution of the structure(which may vary with height). From a data manipulation point of view,the vertical layer boundaries may be defined as the vertical levels atwhich data descriptive of the structure is processed or the layerthickness may be defined as the height separating successive levels ofcross-sectional data that dictate how the structure will be formed. Froma fabrication point of view, depending on the exact fabrication processused, the layer boundaries may be defined in a variety of differentways. For example by planarization levels or effective planarizationlevels (e.g. lapping levels, fly cutting levels, chemical mechanicalpolishing levels, mechanical polishing levels, vertical positions ofstructural and/or sacrificial materials after relatively uniform etchback following a mechanical or chemical mechanical planarizationprocess). For example, by levels at which process steps or operationsare repeated. At levels at which, at least theoretically, lateralextends of structural material can be changes to define newcross-sectional features of a structure.

The terms “adhesion layer”, “seed layer”, “barrier layer”, and the likerefer to coatings of material that are thin in comparison to the layerthickness (e.g. less than 20% of the layer thickness, more preferablyless than 10% of the layer thickness, and even more preferably less than5% of the layer thickness). Such coatings may be applied uniformly overa previously formed layer, they may be applied over a portion of apreviously formed layer and over patterned structural or sacrificialmaterial existing on a current layer so that a non-planar seed layerresults, or they may be selectively applied to only certain locations ona previously formed layer. In the event such coatings arenon-selectively applied they may be removed (1) prior to depositingeither a sacrificial material or structural material as part of acurrent layer or (2) prior to beginning formation of the next layer orthey may remain in place through the layer build up process and thenetched away after formation of a plurality of layers where the thinnessof the coating may be relied on so that undercutting of structuralmaterial on two consecutive layers is not excessive and/or wherethinness of the coatings may be relied on for their destructive removalbetween regions of sacrificial material located on successive layers.

The term “structural layer” shall refer to one or more structuralmaterials deposited during formation of a particular build layer or tothe configuration of such material within the lower and upper boundariesof the layer.

The term “sacrificial layer” shall refer to the one or more sacrificialmaterials deposited during formation of a particular build layer or tothe configuration of such material within the lower and upper boundariesof the layer.

Various embodiments of the invention relate to methods and apparatus forfabricating structures using an EFAB technology-like processes in whichat least one material, e.g. the structural material, is a metal or alloythat is difficult to commercially electrodeposit and/or is difficult tocommercially and directly electrodeposit a metal thereon and which isdeposited by other than electrolytic deposition operations or steps,electroless deposition operations or steps, or metal spraying operationsor steps (e.g., cold spray or plasma spray). Such materials shall bereferred to herein as “HTED metals or alloys”. These alternativedeposition approaches may include vacuum deposition/physical vapordeposition (PVD, e.g., sputtering, evaporation, low temperature arcvapor deposition (e.g., from Vapor Technologies, Inc.), vacuum arcvaporization, reactive evaporation, molecular beam epitaxy, ionizedcluster beam deposition), chemical vapor deposition (CVD, e.g., lowpressure chemical vapor deposition, plasma-enhanced chemical vapordeposition, chemical vapor infiltration (Ultramet, Pacoima, Calif.)),ion-beam-assisted deposition, arc deposition, pulsed-laser deposition,diffusion coating. In some embodiments deposition of a structuralmaterial may occur via melting/sintering/thermal or sonic consolidationof powders or sheets (including ultrasonic consolidation of the sortpracticed by Solidica of Ann Arbor, Mich.), casting. In some embodimentsthe difficult to de, molding processes (e.g., injection or transfermolding) in which the material is applied as a liquid, paste, slurry,semi-solid, or powder, sol-gel processes, mechanical plating, ionplating, electrophoretic deposition (and if required, subsequentconsolidation), spray coating, dip coating, roller coating, and inkjetdeposition.

Structures, components, or devices produced by the method embodiments ofthe invention may include, for example, the fabrication of biomedicaldevices such as surgical instruments and implants (e.g., stents,implantable drug-delivery pumps, pressure sensors, and implantedorthopaedic bone-ingrowth surfaces), inkjet printheads, devices havingdesired shape memory functionality, and the like. Various metals andalloys such as NiTi, Ti, Ta, and certain Liquidmetal® materials producedby Liquid Metal Technologies of Lake Forrest, Calif. may be used asstructural materials (at least on some layers).

Examples of Metals and Alloys for Use in Some Embodiments

In specific embodiments, selected materials may be used in combinationwith selected deposition operations. The selected deposition techniquesare those that are appropriate for materials to be deposited and for theprocess as a whole. Such materials and processes include, for example:

-   -   (1) NiTi and other ‘smart’ alloys (e.g., Nitinol), Ti, and Zr.        These materials may be deposited by sputtering. Sputtering of        relatively thick (several μm to 10 s of μm), relatively        low-stress films of NiTi at a reasonable deposition rates (e.g.,        several μm per hour) is known in the art and is commonly carried        out by such companies as TiNi Alloy of San Leandro, Calif. and        Shape Change Technologies of Thousand Oaks, Calif.    -   (2) Materials such as Ta, Re, W, Mo, and Nb—as well as oxides,        nitrides, carbides, borides, and silicides of these        materials—can be deposited by CVD or chemical vapor        infiltration.    -   (3) Materials such as Al, Mg, Sn, In, Pb, low-melting point        alloys (e.g., Cerro alloys containing Bi, Pb, Sn, and In, or        just Bi and Sn), and solders (e.g., Pb—Sn) may be deposited by        casting or molding the material in molten form.    -   (4) Self-setting (e.g., mercury-containing amalgam) may be        deposited by casting or molding.    -   (5) Materials such as Ti, Mg, and many others may be deposited        in the form of powders which are then melted in place or        sintered (possibly infiltrated with another material which for        biomedical applications may be biocompatible).    -   (6) Materials such as Ti, Mg, and stainless steels may be        applied in sheet form and consolidated through the application        of heat, pressure, and/or sonic vibration.    -   (7) Materials such as Ti may be deposited by low temperature arc        vapor deposition.    -   (8) Materials such as Al may be deposited by mechanical plating.    -   (9) Materials such as Ti, Mg, and Nb may be deposited by        cathodic arc deposition or ion beam-assisted deposition.    -   (10) Proprietary materials such as biocompatible Medcoat 2000        (Electrolizing Corporation of Ohio, Cleveland, Ohio)

Difficult to electrodeposit metals or alloys and/or metals or alloysthat are difficult to electrodeposit onto and which are deposited via anon-electrodeposition process, a non-electroless deposition process, anda non-spray metal deposition process shall be herein termed “HTED metalsor alloys”.

First Group of Embodiments

In a first group of embodiments of the invention a process flow similarto that illustrated in FIGS. 4A-4I may be used with the exception thatthe second material to be deposited is not deposited in an electrolyticmanner (i.e. it is deposited in a non-electrolytic manner) but insteadis deposited in a manner that does not require a conductive base. Inthis group of embodiments the first material is deposited in anelectrolytic manner (e.g. via electroplating, etc.). In some morespecific embodiments in this first group, one of thenon-electrolytically depositable materials (i.e. HTED materials) setforth above is used as the second material to be deposited and itsdeposition occurs in one of the indicated manners.

FIG. 5 provides a block diagram of the major steps in a processaccording to a first group of embodiments where a first structural orsacrificial material is electrolytically deposited and a secondstructural or sacrificial material is an HTED metal or alloy and is thusnon-electrolytically deposited.

Second Group of Embodiments

In a second group of embodiments, the first deposited material is anHTED metal or alloy and is thus deposited in a non-electrolytic mannerwhile the second material is deposited in an electrolytic manner. Thefirst deposited material may be (1) selectively deposited after whichany mask material used in the selective deposition may be removed andthen a second material deposited, (2) blanket deposited over a mold ormasking material and then trimmed back to a desired vertical level (e.g.via a planarization operation or set of operations) to leave a patterneddeposit of the first material after which the masking or mold materialmay be removed and after which a second material may be deposited, or(3) blanket deposited and then selectively patterned (e.g. via etchingthrough a masking material which may be applied after a planarizationoperation or set of operations) and after which a second material may bedeposited. In this second group of embodiments, if the first materialdeposition operation or set of operations results in an over coating ofmaterial on a masking or mold material, prior to deposition of thesecond material, a planarization operation or lift off operation may benecessary to expose the masking or mold material which may then beremoved. In some more specific embodiments of this second group ofembodiments, one of the non-electrolytically depositable materials setforth above is used as the first material to be deposited and itsdeposition occurs in one of the indicated manners. FIGS. 6A-6C provideblock diagrams illustrating various example process flows according tothis second group of embodiments.

FIG. 6A provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is an HTED metal or alloy and thus isnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is selectively deposited.

FIG. 6B provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is an HTED metal or alloy and is thusnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is blanket deposited to cover and fill voids in a maskingmaterial.

FIG. 6C provides a block diagram of the major steps in a processaccording to a second group of embodiments where a first structural orsacrificial material is and HTED metal or alloy and is thusnon-electrolytically deposited and a second structural or sacrificialmaterial is electrolytically deposited and more particularly where thefirst material is blanket deposited and is then patterned to form voidsinto which the second material can be deposited.

Third Group of Embodiments

In a third group of embodiments, both the first and second materials areHTED metals or alloys and thus both materials are deposited innon-electrolytic manners. In this fourth group of embodiments, if thefirst material deposition operation may result in an over-coating ofmaterial on a masking or mold material. Prior to deposition of thesecond material, a planarization operation or lift off operation may beused to expose the masking or mold material which may then be removed.In some more specific embodiments in this fourth group, one of thenon-electrolytically depositable materials set forth above is used asthe first material to be deposited and its deposition occurs in one ofthe indicated manners while another of non-electrolytically depositablematerials set forth above may be used as the second material. FIGS.7A-7C provide block diagrams illustrating various example process flowsaccording to this second group of embodiments.

FIG. 7A provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6A with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

FIG. 7B provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6B with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

FIG. 7C provides a block diagram of the major steps in a processaccording to a third group of embodiments which is similar to theprocess of FIG. 6C with the exception that the second material is alsoan HTED metal or alloy and is thus non-electrolytically deposited.

Fourth Group of Embodiments

In a fourth group of embodiments, three or more materials may bedeposited with one or more of the materials being an HTED metal or alloyand thus not being deposited in an electrolytic manner. In someembodiments of the fourth group of embodiments, structural materials orsacrificial material materials other than HTED materials may bedeposited in non-electrolytic processes. One or more additionalplanarization operations per layer may be required as described above inassociation with the second and fourth groups of embodiments. In thisgroup of embodiments, one, more than one, or all deposited materials maybe selected from the non-electrolytically deposited materialsspecifically set forth above.

FIG. 8 provides a block diagram of the major steps (along with variousalternatives) in a process according to a fourth group of embodimentswhere the number of materials deposited per layer is variable. Inpractice at least one of the materials deposited on one or more layersis an HTED metal or alloy and is thus non-electrolytically deposited.Other processes according to the fourth group of embodiments arepossible. For example, variations in the order of planarizing layers,removing masking material, and removing surface treatment materials arepossible. In other variations, additional steps may be added to providecleaning, additional patterning operations, deposition operations,surface activations, etching of blanket deposited materials and thelike.

Specific Embodiments

FIGS. 9A-9F depict schematic side views of various states of a firstspecific embodiment of the first group of embodiments as applied to anexample structure, where the second material is an HTED metal or alloyand is thus deposited in a non-electrolytic manner. In FIG. 9(A), asuitable substrate 102 has been provided. In this embodiment, as well asin other embodiments, the substrate may be a dielectric (e.g. a ceramicor polymer) with or without a conductive seed layer deposited thereon ora conductive material (e.g. a metal) depending on the specificrequirements of the material or materials to be deposited or on theprocesses used for their deposition or other process used in fabricatingthe structure. For example, if significant temperature differentialswill exist during the fabrication process, then matching coefficients ofthermal expansion as closely as possible between build materials and thesubstrate may be desirable.

In FIG. 9B, a first material 104 (as shown, the sacrificial material)has been selectively deposited (e.g., plated through a photoresist maskwhich has been removed) or alternatively, by wet or dry etching) to formthe indicated example pattern.

In FIG. 9C, a second material 106 (in this example, the structuralmaterial) has been blanket-deposited by one method or another (e.g.,sputtering). The second material adheres at least somewhat to thesubstrate (i.e. the original substrate or to a modified substrate (i.e.to a previously formed layer on the original substrate if the currentlayer is above the one or more previously formed layers). Adhesionbetween layers in this embodiment as well as in the other embodimentsmay be enhanced by diffusion bonding either on a layer-by-layer basis orafter release from the sacrificial material.

In FIG. 9D, the two deposited materials have been planarized to yield asingle layer of controlled thickness, flatness, and surface finish.

In FIG. 9E, the state of the process is shown after additional layershave been formed. These additional layers may be formed by repeating theoperations exemplified in FIGS. 9B-9D a plurality of times or byexercise of one or more different processes. Each layer may have its ownpotentially unique (1) cross sectional configuration, (2) layerthickness, (3) choice of first and second materials, and (4) formationprocesses.

In FIG. 9F, the sacrificial material has been removed, for example byuse of an etchant that minimally damages the structural material,yielding the final or released three-dimensional structure.

In this embodiment, as well as in other embodiments, additionaloperations may be performed during the layer-by-layer build up of thestructure or before or after removal of sacrificial material. Forexample, additional operations may include: (1) cleaning operations, (2)activation operations, (3) annealing operations, (4) hardeningoperations, (5) conformable coating operations, (6) deposition ofadhesion materials, seed layer materials, barrier materials, and thelike. Additional post layer formation operations may include, forexample releasing the structure from the substrate 102 and bonding it orotherwise mounting it on a different substrate, dicing a plurality ofsimultaneously formed structures one from another, packaging thestructure in a hermetic package, forming electrical or mechanicalconnections to the structure.

FIGS. 10A-10F depict schematic side views of various states of a moredetailed example of the first specific embodiment of the second group ofembodiments and in particular of the process of FIG. 6B as applied to anexample structure, where the first material is an HTED metal or alloyand is thus a patterned via non-electrolytic deposition. The HTEDmaterial is deposited into a photoresist mold or mask that has beencreated over the surface of the substrate. FIG. 10A, shows the state ofthe process after a suitable substrate 202 has been provided.

FIG. 10B, depicts the state of the process after a masking material 204(e.g., a planarizable photoresist, possible a fairly hard but removableresist such as SU-8 from MicroChem Inc., Newton, Mass.) has beendeposited and patterned.

In FIG. 100, a first material 206 (e.g. one of the materials set forthabove) has been blanket-deposited by one method or another which causenot only deposition into opening in the masking material but above themasking material as well.

In FIG. 10D, the masking material and the deposited material have beenplanarized (e.g. via lapping or fly cutting, or the like) to expose themasking material so that is may be removed, as has shown in FIG. 10E.

In FIG. 10F, a second material 208 has been blanket-deposited.

In FIG. 10G, the first and second materials have been planarized toyield a single layer of controlled thickness, flatness, and surfacefinish. The planarization level achieved in FIG. 10G may be, andpreferably is, less than that targeted in FIG. 10D.

In FIG. 10H additional layers are shown as having been formed. Theseadditional layers may be formed by repeating the process exemplified inFIGS. 10B-10G a plurality of times or by exercises one or more differentprocesses. Each of these additional layers may have its own(potentially) unique cross section, layer thickness, materials, and mayinvolve different formation operations or orders of performing thoseoperations.

In FIG. 10I, one material (the sacrificial material) is shown as havingbeen removed, yielding the final structure. Due to the use of twoplanarization operations, it may be advantageous to use an initialmasking material thickness that is considerably greater (e.g. 1.2-2.0,or more, times greater) than the final layer thickness required.

FIGS. 11A-11H depict schematic side views of various states of a secondspecific embodiment of the first group of embodiments where the secondmaterial is an HTED metal or alloy and is thus deposited in anon-electrolytic, flowable form (e.g., a liquid, a paste, or a powdernor requiring consolidation). Examples of useable second materialsinclude molten metals and alloys; cast, sprayed, or dippedamorphous/glassy metals such as Liquidmetal® materials (from LiquidmetalTechnologies, Lake Forest, Calif.). In FIG. 11A, a suitable substrate302 has been provided.

In FIG. 11B, a first material 304 (as shown, the sacrificial material)has been electrolytically deposited and patterned. The process resultingin the change of state from FIG. 11A to FIG. 11B may take on a varietyof forms. The process, for example may include (1) applying a maskingmaterial, (2) providing voids in the masking material, selectivelydepositing the first material, and (3) removing the masking material. Asanother example the process may include (1) blanket depositing the firstmaterial, (2) planarizing the first material, (3) applying andpatterning a masking material on the first material, (4) etching intothe first material via voids in the mask, and (5) removing the maskingmaterial. As a third example, the first material may be deposited in adirect write manner or some other maskless and selective depositionprocess.

In FIG. 11C, a second material 306 (in this example, the structuralmaterial and an HTED metal or alloy) has been blanket deposited in anon-electrolytic manner in the form of a liquid, paste, or powder. Sincea relatively thin layer of material is deposited and the substrate(especially if metallic) or previous layer tends to be quite thermallyconductive, materials that might normally solidify with a crystallinemicrostructure may be induced to solidify as an amorphous materialinstead, which can benefit strength, hardness, corrosionresistance/biocompatibility, elasticity, etc.

In FIG. 11D, a doctor blade 308 (or other smoothing/trimming device,e.g. a counter rotating roller) is depicted as being used to removeexcess flowable material. Alternatively or in addition to the doctorblade approach, a plate 312 pressed against the material can be used toremove excess material, as shown in FIG. 11E. The result of removing theexcess flowable material is show in FIG. 11F.

Next (not shown), the material would typically be at least partiallysolidified (e.g., through cooling, thermal polymerization, radiationbased polymerization, other curing, solvent evaporation, and the like).If such solidification is not required to allow planarization in thenext step, the solidification operation may be skipped or delayed. Ifthe material will undergo a shrinkage upon solidification, it may bedesirable to ensure it has some excess thickness prior to solidificationand planarization to accommodate for this shrinkage alternatively, aftersolidification the operations of FIGS. 11C-11F may be repeated toincrease the height of the second material prior to considering theformation of the current layer to be completed.

In FIG. 11G, the two materials (i.e. the first and second materials)have been planarized to yield a completed layer. Depending on thematerials involved, the level of accuracy required, and the surfacefinish required, the planarization process may take on a variety offorms. For example, planarization may occur via grinding, via singlestage or multistage lapping, lapping and polishing, lapping followed byetching, lapping followed by etching and polishing, chemical mechanicalpolishing (CMP), fly cutting using a diamond tipped tool, and/or thelike.

In FIG. 11H, the state of the process is shown after five additionallayers have been formed either by repeating the process exemplified inFIGS. 11B-11G or by use of one or more other processes.

In FIG. 11I, the sacrificial material has been removed, yielding thefinal structure formed from a single structural material.

FIGS. 12A-12H depict schematic side views of various states of a thirdspecific embodiment of the first group of embodiments where the firstmaterial is deposited electrolytically and the second material is anHTED metal or alloy and is deposited in a powder form that requiresconsolidation.

In FIG. 12A, the state of the process is shown after a suitablesubstrate 402 has been provided.

In FIG. 12B, a first material 404 (as shown, the sacrificial material)has been patterned (e.g. via selectively deposition, blanket depositionfollowed by selective removal, or blanket deposition over a maskingmaterial followed by removal of the masking material and any overlayingfirst material).

In FIG. 12C, a second material 406 (in this example, the structuralmaterial) in the form of a powder has been blanket-deposited. In thisembodiment the powder is applied to a thickness that allows forshrinkage in volume as it is pressed and consolidated.

In FIG. 12D, a ram 408 capable of applying compressive pressure to thematerial is used to compress it. Not shown is an optional step to removeexcess powder similar to those shown in FIGS. 11D and 11E. Afterconsolidation, most or all of the void space between the powderparticles may have been removed, forming a mostly non-porous mass.Alternatively, residual pores may remain, which may be infiltrated withthe same or a different material before continuing further (e.g., on alayer-by-layer basis) or later, after release of sacrificial material.If desired; however, variations of this embodiment may be used to createa porous structure.

The result of compacting the material is show in FIG. 12E where material406 has been converted into material 406′. In some alternativeembodiments, instead of a ram, a flexible medium able to apply pressurecould be used and cold or hot isostatic pressing used for thecompaction. In some variations of this embodiment, compaction may causeconsolidation of the particles into a cohesive mass while in othervariations one or more additional processing steps may be used toconsolidate the compacted particles. This additional step or steps maybe dependent on the properties of the particles themselves. For example,particles that are formed from a meltable material or are coated with ameltable material may be converted via application of heat, whereasparticles that are coated with a radiation curable material or volatilematerial may be consolidated by exposure to radiation or vacuum (i.e. toaid in removal of the volatile material). In still other variations,consolidation may occur by infiltrating the particles with a flowablebinding agent or with a flowable filler material.

In FIG. 12F, the two materials are shown as having been planarized.

In FIG. 12G, the state of the process is shown after additional layersare formed. These additional layer may be formed by repeating theoperations of FIGS. 12B-12F a plurality of times using appropriatematerials and cross-sectional patterns or they may be formed usingdifferent process steps.

In FIG. 12H, the sacrificial material has been removed, yielding astructure which may be in final form, or it may be ready for furtherprocessing. For example, additional processing may include infiltratingpores in the structure with a filler material. Alternatively, the poresand voids can be removed by further heating or by cold or hot isostaticpressing. In an alternative to the embodiment of FIGS. 12A-12H, nocompression may be performed but instead a process of filling pores maybe used such as that described in U.S. patent application Ser. No.10/697,597 entitled “EFAB Method and Apparatus Including Spray Metal orPowder Coating Processes” or in U.S. Pat. No. 3,823,002, entitled“Precision Molded Refractory Articles,” issued July 1974 to Kirby etal.; U.S. Pat. No. 3,929,476, entitled “Precision Molded RefractoryArticles and Method of Making,” issued December 1975 to Kirby et al.;U.S. Pat. No. 4,327,156, entitled “Infiltrated Powdered Metal CompositesArticle,” issued April 1982 to Dillon et al.; U.S. Pat. No. 4,373,127,entitled “EDM Electrodes,” issued February 1983 to Hasket et al.; U.S.Pat. No. 4,432,449, entitled “Infiltrated Molded Articles of SphericalNon-Refractory Metal Powders,” issued February 1984 to Dillon et al.;U.S. Pat. No. 4,455,354, entitled “Dimensionally-Controlled CobaltContaining Precision Molded Metal Article,” issued June 1984 to Dillonet al.; U.S. Pat. No. 4,469,654, entitled “EDM Electrodes,” issuedSeptember 1984 to Hasket et al.; U.S. Pat. No. 4,491,558, entitled“Austenitic Manganese Steel Containing Composite Article,” issuedJanuary 1985, to Gardner; U.S. Pat. No. 4,554,218, entitled “InfiltratedPowdered Metal Composite Article,” issued November 1985, to Gardener etal.; U.S. Pat. No. 5,507,336, entitled “Method of Constructing FullyDense Metal Molds and Parts,” issued to Tobin; or U.S. Pat. No.6,224,816, entitled “Molding Method, Apparatus, and Device Including Useof Powder Metal Technology for Forming a Molding Tool with ThermalControl Elements”, issued May 2001, to Hull, et al. Each of these patentapplications and patents is incorporated herein by reference.

FIGS. 13A-13H depict schematic side views of various states of a fourthspecific embodiment of the first group of embodiments as applied to aspecific example structure where the second material is an HTED metal oralloy and is deposited in sheet form, then deformed mechanically,sonically, and/or thermally.

In FIG. 13A, the state of the process is shown after a suitablesubstrate 502 has been provided.

In FIG. 13B, the state of the process is shown after a first material504 (as shown, the sacrificial material) has been patterned.

In FIG. 13C, a second material 506 (in this example, the structuralmaterial) in the form of a sheet has been laid on top of the partiallyformed layer (i.e. on top of the first material).

In FIG. 13D, a ram 508 capable of applying compressive pressure, heat,and/or sonic vibration to the material is used to deform it such that itflows into the apertures in the first material with minimal voids andadheres at least somewhat to the first deposited material and to theprevious layer (or substrate), for example, by cold welding, diffusionbonding, or the like. In some variations of the embodiment, thecompression may be performed under vacuum. Alternatively, instead of aram, a flexible medium able to apply pressure could be used and cold orhot isostatic pressing used for the deformation.

The state of the process that after the deformation is completed isshown in FIG. 13E.

In FIG. 13F, the two materials have been planarized and excesssqueezed-out material has been trimmed off if required.

In FIG. 13G, the state of the process is shown after formation of aplurality of additional layers. The additional layers may be formed viarepetitions of the process exemplified in FIGS. 13B-13F or via someother process.

In FIG. 13H, the sacrificial material has been removed, yielding thefinal structure.

FIGS. 14A-14N depict various states of a process for forming athree-dimensional structure according to a fifth specific embodiment ofthe first group of embodiments of the invention in which multilayerstructures of nickel titanium (NiTi), tantalum (Ta), or titanium (Ti) orother material (HTED metal) that is difficult to plate onto can befabricated. In the remaining discussion of this embodiment, it will beassumed that NiTi is the structural material though it should beunderstood that it may be replaced with one of this other materials invariations of this embodiment. This embodiment uses anodic activation ofNiTi located on an immediately preceding layer possibly in combinationwith other processes such as cathodic activation to prepare NiTi forreceiving electrodeposited sacrificial metal (e.g. copper) with goodadhesion during the formation of a current layer. FIGS. 14A-14Nillustrate a process in which a NiTi structure is fabricated over acompound substrate that includes a sacrificial material located on abase substrate so as to enable ultimate separation of the structure fromthe base substrate. In variations of this embodiment structures may bebuilt that adhere to a base substrate or to a compound substrate thatincludes a non-sacrificial coating (e.g., Au or Ni) on a base substrate.

FIG. 14A shows the state of the process after substrate 602 (moreparticularly a base substrate) is supplied. The substrate 602 mayinclude one or more previously formed multi-material layers or singlematerial coatings.

In FIG. 14B the state of the process is shown after a coating ormono-material layer of sacrificial material 604 (e.g. copper) has beendeposited and planarized (if required).

In FIG. 14C the state of the process is shown after a photoresist 606-1or other masking material has been deposited and patterned onsacrificial material 604-0 on substrate 602.

In FIG. 14D the state of the process is shown after a sacrificialmaterial 608 (e.g. copper) has been selectively electrodeposited withinvoids or openings in the photoresist 606. Sacrificial material 604-1 maybe different or the same as sacrificial material 604-0.

In FIG. 14E the state of the process is shown after the photoresist606-1 has been removed.

In FIG. 14F the state of the process is shown after a structuralmaterial 612-1 (e.g. NiTi) has been blanket deposited.

In FIG. 14G, the first layer comprising both a sacrificial material anda structural material has been planarized. Since this first layer wasnot formed over a surface that was hard to plate onto, there was no needto take special steps to prepare the surface to be plated withsacrificial material. However, in general, the cross-sectional geometryof the second and subsequent layers will be such that sacrificialmaterial needs to be deposited at least in part over underlyingstructural material (e.g. NiTi) which may require surface preparation.It is understood that the formation of some layers may involvesacrificial material being deposited over only sacrificial material onthe previous layer and in such cases, when they are recognized ordetected, it may be possible to forego any special surface preparationsteps. It is also understood that the formation of some layers mayinvolve sacrificial material being deposited over both sacrificialmaterial and structural material but where the majority of the edges ofsacrificial material only contact regions of sacrificial material andwhen such situations are recognized or detected, it may be possible toforego any special surface preparation steps.

In FIG. 14H the process is shown after preparation for forming a secondlayer on the first layer is initiated by the depositing and patterningof a photoresist 606-2. As shown in FIG. 14H, at least some of theopenings 614 through the photoresist reveal exposed NiTi on the previouslayer. Sacrificial material will be deposited into these openings. FIG.14I shows the state of the process after a process of activating andpreparing the surface of the previous layer has been performed. Invariations of this embodiment, the activation comprises anodicactivation followed immediately by cathodic activation, both in a 15%(volume) hydrochloric acid solution. When performing such activation,the use of noble metal electrodes (first as a cathode and then as ananode) such as platinum-coated titanium may be preferred. As examples,anodic (i.e., the wafer is the anode) and cathodic (i.e., the wafer isthe cathode) current densities of 80 mA/cm² for one minute may be usedfor activation. When anodic activation is used, some dissolution 616-1of the sacrificial material 604-1 may result as shown in FIG. 14I.Furthermore some undercutting 618-1 of the photoresist may occur. It isanticipated that little or none of the NiTi will be dissolved.

In FIG. 14J, sacrificial material 604-2 (e.g. Cu) for the second layerhas been deposited (e.g., from an acid Cu plating bath at a currentdensity of 20 mA/cm²) through the apertures of the photoresist. Ideallythe sacrificial material is deposited as soon as possible afteractivating the surface to minimize the risk of re-oxidation (placing thewafer in an inert gas after activation may be useful in this regard).

In FIG. 14K the state of the process is shown after photoresist 606-2has been stripped.

In FIG. 14L the state of the process is shown after the structuralmaterial 612-2 (e.g. NiTi) has been deposited.

In FIG. 14M the state of the process is shown after the planarization ofthe sacrificial material 606-2 and structural material 612-2 depositedin association with formation of the second layer has been planarized tocomplete formation of the second layer.

Finally, in FIG. 14N the structure 622 formed of structural material612-1 and 612-2 has been released by etching away sacrificial materials604-0, 604-1, and 604-2. In some variations of this embodiment thestructural material deposited on each layer may be the same materialwhile in other variations of the embodiment, the structural materialdeposited on one or more layers may be different from that deposited onone or more other layers. In some variations of this embodiment thesacrificial material 604-0 deposited on the base substrate and thesacrificial material 604-1 and 604-2 forming part of each layer may bethe same material while in other variations of the embodiment, thesacrificial material deposited on the base substrate and/or on one ormore layers may be different from that deposited on one or more otherlayers.

Bubbles produced during both cathodic and anodic activation inpreparation for depositing sacrificial material in association with acurrent layer may get trapped in small openings in the photoresist, thuspreventing the structural material on the previous layer from beingproperly activated in some areas. In some variations of this embodiment,the use of mechanical agitation of the activation bath,ultrasonic/megasonic agitation of the bath, vacuum or low-pressuredegassing of the bath, and/or the addition of a surfactant to the bathmay be used.

In some variations of this embodiment, different surface preparations(e.g., activation processes) may be used for different layers beforedepositing sacrificial material such as Cu. In other embodiments,surface activation may be used after deposition of the sacrificialmaterial and prior to deposition of structural material to improveadhesion of the structural material on a current layer to thatassociated with the preceding layer or to improve electricalconductivity through structural material a crossed layer boundaries.

Some sacrificial material dissolution (e.g., FIG. 14I) during structuralmaterial activation prior to sacrificial material deposition may beacceptable since the sacrificial material that will be deposited afterthe activation (e.g., FIG. 14J) can fill in or substantially fill in anymissing material. Depending on the geometry, however, the dissolutionmay be excessive. It can, for example, cause delamination of photoresistby undercutting photoresist that is mostly or completely supported byCu. There may also be regions formed of undercut (e.g., larger thanshown in FIG. 14I) that do not get sacrificial material plated backduring the subsequent deposition because the photoresist overhangs,shadows, or masks the undercut region 618-1 too much. While some voidsmay be acceptable in the sacrificial material (e.g. as long as thesacrificial material is electrically continuous and mechanicallystrong), structural material may, in some cases, be deposited into thevoids, forming a protruding defect on the underside of a structuralfeature. Therefore in some embodiments (e.g. during formation ofselected layers), methods which reduce or eliminate sacrificial materialdissolution may be used. In some such embodiments, anodic activationtime or current density may be reduced, possibly with cathodicactivation following the anodic activation and with the cathodicactivation being applied for a longer time and/or at a higher currentdensity. In some alternative embodiments, no anodic activation or areduced amount of anodic activation may be used, with a copper strikeperformed after cathodic activation (e.g., in an HCl bath) instead.

In some other alternative embodiments, no anodic activation may be usedor a reduced amount of anodic activation may be used, with a nickelstrike performed after cathodic activation. Although thebiocompatibility of nickel for medical device applications may be lessthan desirable, the amount of nickel that is used is small. Moreover, insome such embodiments, before (or preferably, after) release ofsacrificial material, heat treatment of the structure will cause thethin nickel and the NiTi (or other structural material) tointer-diffuse, reducing or eliminating the quantity of pure Ni that ispresent in the final product. Heat treatment is generally desired in anycase to transform sputtered amorphous NiTi into its crystalline form,and in some embodiments the two results may be achieved during the sameheat-treatment process.

In the case of building structures with Tantalum (Ta) as a structuralmaterial, hydrofluoric acid (HF) may be used by itself to remove Taoxide in preparation for plating sacrificial material such as Cu. Insome embodiments, application of HF followed by a strike (nickel orcopper) may be used. In some embodiments, HF may be used as the bath inwhich anodic and/or cathodic activation, either with or without a nickelor copper strike, may be performed.

In some alternative embodiments, to minimize risk of sacrificialmaterial dissolution, the previous layer may be patterned (e.g., withphotoresist) so that only those regions of structural material (e.g.NiTi) that are to be plated with sacrificial material during formationof a current layer are exposed to the electrochemical activationtreatment.

In still other embodiments, the structural material (e.g. NiTi) may becoated with a material that can be electroplated onto. This coating mayoccur via a vacuum deposition process. In some embodiments, thismaterial is the one of the sacrificial materials used to in fabricatinglayers. In others, it is a different sacrificial material which iseither removed by a similar process as that used to remove the primarysacrificial material, or by a different process. In others, it is anon-sacrificial material that remains and is acceptable as part of thefinal structure (e.g., for some applications it may need to bebiocompatible).

FIGS. 15A-15H depict various states of a process for forming athree-dimensional structure according to a sixth specific embodiment ofthe first group of embodiments of the invention in which a coating ofthe sacrificial material to be electrodeposited over a previously formedlayer that contains or may contain a structural material that is hard toelectroplate over (i.e. an HTED metal, e.g. NiTi) is first applied usingvacuum processing and then increased in height via electroplating.

FIG. 15A depicts the state of the process after partial formation of astructure 702. That is FIG. 15A depicts the state of the process afterone or more multi-material layers 702 comprising a partially formedstructure have been formed on a substrate where the most recently formedlayer includes a structural material that is difficult to electroplateover. In this embodiment, it is assumed that layers 1 to N−1 havealready been formed as part of partially formed structure 702 and thatthe next layer to be formed is layer N.

FIG. 15B depicts the state of the process after a masking material 706-N(e.g., photoresist) has been deposited and patterned onto the previouslyformed layers 702 of the partially formed structure. The maskingmaterial 706-N is preferably is of a kind that can be processed to yieldvertical sidewalls.

In FIG. 15C, a first material (e.g., Cu) 708-N has been vacuum deposited(e.g., by sputtering or evaporation) onto the previously formed layers702 and over the masking material to form a thin portion of the Nthlayer. This vacuum-deposited material can adhere well to the structuralmaterial (e.g. NiTi) or materials and sacrificial material or materialsforming part of the previously formed layer. Adhesion, and potentiallyconductivity, can be enhanced further by performing a plasma etch, backsputtering, or other treatment to remove any oxide layer prior to thevacuum deposition of first material 708-N process. Any such treatment ispreferably followed by deposition without breaking vacuum in thedeposition chamber. However, if desired, an adhesion film (not shown)can be deposited prior to the vacuum deposition of the first material708-N, preferably without breaking vacuum, and preferably of a material(e.g., TiW) that can be removed using the same etchant as is used toremove the sacrificial material (e.g., Cu).

FIGS. 15D-15F and FIGS. 15D′-15F′ illustrate two alternative sequencesof steps that may be carried out after vacuum depositing the firstmaterial 608-N.

FIG. 15D depicts the state of the process after the first material 708-Noverlying the masking material has been removed (e.g., by planarization,possibly using diamond machining), leaving behind a thickness sufficientto allow for an additional planarization step later. This removal stepexposes the top surface of the masking material 706-N, allowing forremoval of this material later.

FIG. 15E depicts the state of the process after a relatively thickdeposit of the first material 608-N via electrodeposition (e.g. having athickness that yields a total deposition height greater than the finallayer thickness desired for the Nth layer). In some alternativeembodiments this material may be different from the vacuum depositedmaterial. In this embodiment, it is presumed that the previous layer isconductive. In variations of this embodiment, if the previously layer isnot conductive, it may be made conductive by deposition of a conductivecoating material or materials (e.g., Ti/Au).

FIG. 15F depicts the state of the process after the masking material706-N has been removed (e.g., by chemical stripping).

FIG. 15D′ depicts the state of the process, along an alternative processbranch, after a relatively thick deposit of the first material 708-N hasbeen deposited to a depth typically in excess of the final layerthickness for the Nth layer. Although the previous layer may beconductive, this is not required since the vacuum-deposited firstmaterial forms a continuous plating base.

FIG. 15E′ depicts the state of the process after the vacuum depositedfirst material 708-N, the electrodeposited first material 708-N, and themasking material 706-N have been planarized (e.g., by diamondmachining), leaving behind a thickness typically sufficient to allow foran additional planarization step later that will set the boundarylevel/height of the Nth layer. This planarization step exposes the topsurface of the masking material, allowing removal (e.g., by chemicalstripping) as shown in FIG. 15F′.

FIG. 15G depicts the state of the process after the second material712-N, i.e. the structural material (e.g. NiTi), has beenblanket-deposited filling in the voids apertures 714-N in the firstmaterial.

FIG. 15H depicts the state of the process after the second material712-N, the layer has been planarized to yield the desired thickness,planarity, and surface finish. Planarization may for example occur viadiamond fly cutting, lapping, a combination of mechanical trimming andpolishing, along with chemical etching, and the like. The steps shown inFIGS. 15B-15H can be repeated, with different patterns on each layer ifdesired, or other layer forming operations may be performed to addadditional layers above layer N so as to build up a multi-layerstructure from one or more structural materials and with supportingsacrificial material that will eventually be removed.

FIGS. 16A-16I depict various states of a process for forming athree-dimensional structure according to a seventh specific embodimentof the first group of embodiments of the invention in which a coating ofthe sacrificial material, to be electrodeposited, over a previouslyformed layer that contains or may contain a structural material that ishard to electroplate over (i.e. an HTED metal, e.g. NiTi) is firstapplied to selected portions of a previously formed layer via voids in amasking material and prior to thickening the coating of the firstmaterial, a lift off process is used to remove the vacuum depositedmaterial from above the masking material.

FIG. 16A depicts the state of the process after a partially formedstructure 802 is created and supplied for further processing. In thisembodiment, it is assumed that layers 1 to N−1 have already been formedas part of partially formed structure 802 and that the next layer to beformed is layer N.

FIG. 16B depicts the state of the process after a masking material 806-N(e.g., photoresist) has been deposited and patterned onto the providedpartially formed structure 802. The masking material is preferably of atype that provides an undercut sidewall geometry (not shown) whenprocessed appropriately, and may be quite thin (the figure is not toscale). As before, removal of any oxide by plasma, back sputtering, orchemical cleaning, for example, may be done prior to vacuum depositionof the first material

FIG. 16C depicts the state of the process after a first material 808-N(i.e. a sacrificial material, e.g., Cu) has been vacuum deposited usinga directional deposition process such as evaporation) onto the previouslayer and over the masking material. If desired, an adhesion layer suchas TiW can be deposited prior to the deposition of the first material808-N and after any treatment process. Because of the undercut geometryof the masking material, the deposited material first material 808-Ndoes not completely coat the sidewalls of the masking material.

FIG. 16D depicts the state of the process after the masking material hasbeen stripped via a lift off process along with that portion of thefirst material 808-N that overlaid it. After the lift off process theonly regions of first material remaining on the Nth layer are thoseregions where the first material was deposited directly onto thepartially formed structure 802.

FIG. 16E depicts the state of the process after another masking material816-N has been deposited and patterned in substantially the same patternas the initial masking material 806-N. This masking material, however,preferably is of a kind that can be processed to yield verticalsidewalls.

FIG. 16F depicts the state of the process after a relatively thickdeposit of the first material 808-N has been deposited to a depth inexcess of the final layer thickness desired.

FIG. 16G depicts the state of the process after the masking material816-N has been removed (e.g., by chemical stripping).

FIG. 16H depicts the state of the process after a second material (i.e.a structural material, e.g. NiTi) has been blanket-deposited, filling inthe apertures 812 in the first material where masking material 806-N and816-N were previously located.

FIG. 16I depicts the state of the process after the deposits made inassociation with the Nth layer have been planarized to set the boundaryof the Nth layer at a desired thickness, planarity, and surface finish.The steps shown in FIGS. 16B-16J can be repeated, with differentpatterns on each layer if desired, or other layer forming operations maybe performed to add additional layers above layer N so as to build up amulti-layer structure from one or more structural materials and withsupporting sacrificial material that will eventually be removed.

FIGS. 17A-17J depict various states of a process for forming athree-dimensional structure according to an eighth specific embodimentof the first group of embodiments of the invention in which a coating ofthe sacrificial material, to be electrodeposited, over a previouslyformed layer that contains or may contain a structural material that ishard to electroplate over (i.e. an HTED metal, e.g. NiTi) is firstapplied over the entire previous layer via a blanket vacuum depositionafter which masking material is applied and the material patterned viaetching.

FIG. 17A depicts the state of the process after a partially formedstructure 902 is supplied. In this embodiment, it is assumed that layers1 to N−1 have already been formed as part of partially formed structure902 and that the next layer to be formed is layer N. As discussed abovewith regard to the embodiments of FIGS. 15A-15H and 16A-16I, beforevacuum deposition of the first material 908-N, removal of any oxide onthe previously formed layer, and more particularly from structuralmaterial on the previously formed layer, may occur via plasma etching,back sputtering, or chemical cleaning, or the like.

FIG. 17B depicts the state of the process after a first material 908-N(e.g., Cu) has been vacuum deposited onto the previous layer (i.e. layerN−1). If desired, an adhesion layer such as TiW can be deposited priorto the vacuum deposition of material 908-N.

FIG. 17C depicts the state of the process after a masking material 906-N(e.g., photoresist) has been deposited and patterned onto the previouslayer.

FIG. 17D, depicts the state of the process after the first material (andthe adhesion layer, if any) has been selectively etched using themasking material as a mask, resulting in a patterned film of firstmaterial (In FIG. 17E) overlaying regions where sacrificial material forlayer N is to be located. In variations of this embodiment, the vacuumdeposited material need only remain in those regions where sacrificialmaterial overlays structural material that is hard to plate on that islocated on layer N−1.

FIG. 17F depicts the state of the process after another masking material916-N has been deposited and patterned. This material is preferably isof a kind that can be processed to yield vertical sidewalls. Thismaterial is patterned to locate openings over locations wheresacrificial material 908-2 is to be thickened.

FIG. 17G depicts the state of the process after a relatively thickdeposit of the first material 908-N has been deposited to a depth inexcess of the final desired layer thickness.

FIG. 17H depicts the state of the process after, the masking material916-N has been removed (e.g., by chemical stripping).

FIG. 17I depicts the state of the process after a second material (i.e.structural material, e.g. NiTi) has been blanket-deposited, filling inthe apertures 912 in the first material 908-N.

FIG. 17J depicts the state of the process after the layer has beenplanarized to yield the desired thickness, planarity, and surfacefinish. The steps shown in FIGS. 17B-17J can be repeated, with differentpatterns on each layer if desired, or other layer forming operations maybe performed to add additional layers above layer N so as to build up amulti-layer structure from one or more structural materials and withsupporting sacrificial material that will eventually be removed.

Additional Embodiments

Though the specific embodiments addressed explicitly herein have focusedprimarily on the first group of embodiments, it will be clear to thoseof skill in the art that these embodiments may be modified or combinedto derive new embodiments within the first group of embodiments as wellas to derive specific embodiments that fall within the second throughfifth groups of embodiments. For example, when the second material to bedeposited on a given layer is to be electrodeposited while the firstmaterial to be deposited on the layer is an HTED material, preparationof the surface of the previously formed layer for receiving theelectrodeposition of the second material may be delay until afterdeposition of the HTED material. Sputtered seed layer deposition mayoccur in a planar manner prior to deposition of the HTED material or ina non-planar manner such that it overlaying the HTED material as well ascoating exposed regions of the last formed layer.

Though the embodiments have been described using the terms first andsecond materials, it should be understood that these materials do notnecessarily have to be the first and second materials deposited on alayer or even consecutively deposited materials. In absence of otherlimiting features, the terms first and second should be considered toonly imply that the first material was deposited prior to the depositionof the second material.

In the first through fourth groups of embodiments noted above, the firstmaterial may be a sacrificial material and the second material may be astructural material while in other embodiments, the first material maybe a structural material and the second material may be a sacrificialmaterial, while in still further alternative embodiments, both materialsmay be retained as structural materials. In the fifth group ofembodiments, one or more materials may be structural material with anyremaining materials being a sacrificial material.

In variations of the above noted groups of embodiments and specificembodiments where one material is to be deposited by electrolyticdeposition, a seed layer (i.e. coating) and possibly an adhesion layer(i.e. coating) may be applied to an existing base (i.e. a previouslyformed layer, substrate, or previously deposited material forming partof the current layer) if the base is not sufficiently conductive toallow electrodeposition onto it or to which adhesion of theelectrolytically deposited material is not adequate. Coatings may alsobe used to provide a barrier between two materials in case they areincompatible, would form undesirable intermetallic compounds, etc. Also,coatings in the form of a thin ‘strike’ may be used to facilitateelectrodeposition of subsequent thicker deposits. The strike materialmay preferably, but not necessarily, be of the same material that willbe thickly deposited over it.

Certain materials (typically structural materials) may benefit from coldworking or similar mechanical action to improve properties such asstrength. This can be achieved on a layer-by-layer basis by applyingmechanical force (e.g., compressive force) to the material either afterdeposition or after planarization, or can be achieved after all layersare formed, either before or after release of sacrificial material. Tofacilitate the applying this force on a layer-by-layer basis, it may beadvantageous to first partly planarize the layer (e.g. at a height thatis above the desired layer boundary level), then apply the force, thenfinalize the planarization to achieve the final layer thickness,flatness, and/or surface finish (i.e. to set achieve the desiredboundary level between the current layer and a subsequent layer to beformed). To allow for the effects of this force on layer thickness ortopography, a thicker-than-normal deposit may be provided, with anyexcess removed through planarization. Also, since the force may causefeatures to widen or narrow compared with their intended dimensions,these dimensions can be precompensated in the original design orotherwise, to allow for this. Furthermore, if the sidewall angle of thelayers is distorted by the force, this too may be precompensated, e.g.,during the lithography stage, by tailoring the sidewall angle of thephotoresist or similar material. The force may be provided by staticpressure (e.g., contact with high-pressure ram or rollers) or by impact(shot peening, tumbling in a barrel with appropriate media,sandblasting, fluid jet, etc.). Layers deposited early in the buildprocess (i.e., lower layers) may need less working than layers depositedlater (i.e., upper layers) since they may be worked somewhat when thelater layers are worked, by transmission of force through the upperlayers. In some embodiments, heat treatment may be performed after thecold working is performed.

Prior to the deposition step shown in FIGS. 9B and 10B and especially ifthis deposition is by electrolytic means, it may be necessary tocondition the surface of the previous layer to allow for satisfactoryadhesion. Similarly, prior to the deposition steps of FIGS. 9C and 10C,conditioning of the previous layer may be needed. Such conditioning mayinvolve electrolytic or chemical removal of oxide films, cleaning,degreasing, activation, etc. It may be important that the conditioningprocess does not degrade or damage the surface of other materials (e.g.,the sacrificial material) that may be on the previous layer.

In some specific variations of the process exemplified in FIG. 9A-9F thefirst material deposited is the sacrificial material and includes Cu,Sn, of Zn while the second material is the structural material that issupplied via sputtering and includes nickel titanium (NiTi). In anotherspecific variation of the embodiment exemplified in FIGS. 9A-9F, thefirst material is the sacrificial material which is electrolyticallydeposited Cu, Sn, or Zn while the second material is the structuralmaterial that is deposited via chemical vapor deposition (CVD) orchemical vapor-infiltrated deposition and include tantalum (Ta). Instill another specific variation of the embodiment exemplified in FIGS.9A-9F, the first material is the sacrificial material and includes Cu,Sn, or Zn while the second material is the structural material which isdeposited via casting and includes Mg. In still other specificvariations of the embodiment exemplified in FIGS. 9A-9F Ta, Fe, Mo, orstainless steel may be used as sacrificial materials.

In specific variations of the other embodiments and groups ofembodiments set forth above, the specific variations discussed withreference to FIGS. 9A-9F may be implemented, mutatis mutandis.

In some embodiments, the aspect ratio (height/width) of apertures in thefirst (patterned) material may need to be kept below a particular value(e.g. height to width <1 or 1.5), and the minimum width of apertures mayneed to be kept above a particular value (e.g. width>5, 10, 20, or even50 microns), such that voids are not produced in the second material.For PVD and possibly CVD deposition, rotating the substrate (e.g., aboutone or more axes that are parallel to the front surface of thesubstrate) may be useful in allowing an increase in aspect ratio or adecrease in minimum width.

In some embodiments, the first (patterned) material may need specialcharacteristics to be compatible with subsequent processing, such asmechanical strength (e.g., for the methods shown in FIG. 12A-12H or13A-13H), temperature stability, and/or high-temperature oxidationresistance (e.g., for the method shown in FIG. 11A-11H). In otherembodiments, the first and/or second material may need to havecoefficients of thermal expansion matched closely to one another and/orto the substrate particularly when substrate area become large and moreparticularly when length of structural material regions become large. Insome embodiments, it may be desirable to form lanes (e.g. dicing lanes,which may or may not be eventually diced) that separate individual diewhere the lanes are filled with structural material (e.g. Ta) or leftfree of material to minimize stress induced by the sacrificial materialduring temperature variations that may occur during processing (e.g.when cooling down from an 800° C. Ta deposition process). Lanes may beleft free of material by use of shielding (e.g. shadow masks that arelaid above openings in a first deposited material) to inhibit materialdeposition followed by a lift off operation if necessary to remove theshielding.

In many embodiments, the substrate may include a release layer (e.g. afirst layer or coating deposited on an initial substrate may be formedcompletely from a sacrificial material) so that a permanent or initialpart of the substrate may be separated from structural material that isdeposited during the formation of layers. Alternatively, the entiresubstrate may be formed from a sacrificial material that can be removed.This may be desirable for applications where free structures are needed.

In the various embodiments, the one or more structural materials and oneor more sacrificial materials should be selected such that they arecompatible. For example, the sacrificial material may be selected so itcan be removed (e.g., by chemical etching or melting) with respect tothe structural material with little or no degradation of the latter. Thetwo materials may be selected so that they can be co-planarized withminimal recession, dishing, smearing, etc. of one material with respectto another during selected planarization operations. Also, the twomaterials may (unless this is desired) be selected so that they do notform intermetallic compounds at their mutual interface.

Additional Teachings:

Thermal Processing:

Thermal processing of structures produced by some embodiments of theinvention may be needed or desired. For example, diffusion bonding orother forms of heating, including low-temperature heating may be used toenhance inter-layer adhesion as already noted. Some materials mayrequire heat treatment to obtain the desired properties. For example,NiTi is deposited by sputtering typically in an amorphous form andrequires heat treatment to transform it into a crystalline form. Heattreatment may be used to simultaneously enhance inter-layer adhesion andtransform sputtered NiTi into a crystalline form. Prolonged heattreatment, beyond what is normally required to transform amorphousmaterial, may be used to provide additional inter-layer strength. Heattreatment may also be used to diffusion bond togetherseparately-fabricated components of a device, in combination withtransforming the components from an amorphous to a crystalline state.Heat treatment may also be used to set the shape of a shape memory alloysuch as NiTi, or adjust the transition temperature. In all such caseswhere thermal processing is needed, it may be preferable to release thestructure (i.e., remove the sacrificial material from the structuralmaterial) and/or separate the structure from the substrate on which itis built, prior to thermal processing, to avoid distortion and damagedue to differences in the coefficients of thermal expansion betweendifferent materials.

Preparing Oxidized Surfaces for Sacrificial Material Plating

NiTi (e.g., Nitinol) is a biocompatible, non-magnetic metal alloy that,depending on composition, can exhibit superelastic and shape memoryproperties that make it useful for many applications (including medicaldevices) as a structural material for the EFAB® microfabricationtechnology. However, it has a stable (titanium) oxide layer on itssurface, which makes it a challenge to achieve good adhesion whendepositing a sacrificial material such as Cu on top of NiTi on aprevious layer, as is generally required when building multi-layerstructures. Similar problems may be found with other materials such asTa and Ti, and the methods of this invention are applicable to them aswell.

To obtain good adhesion between an electrodeposited material and NiTi onthe previous layer, the NiTi may be pretreated in some embodiments usingelectrochemical activation so that the surfaces to be plated are cleanand active prior to electrodeposition. Adhesion of a sacrificial metal(e.g. copper) to structural metal (NiTi) need not be extremely good, butgenerally needs to be good enough that no delamination of materialoccurs during wafer processing, such as during planarization when thematerial is subject to mechanical forces.

Sputtering of Materials

When depositing materials (e.g., NiTi) in a vacuum chamber usingprocesses such as sputtering, it may be important to mask off certainareas of the wafer, especially if the material is to be deposited in aselective fashion. For example, pads on the wafer surface may beprovided for making measurements associated with endpointing of theplanarization process. More information about such pads and measurementprocesses can be found in U.S. patent application Ser. No. 11/029,220,filed Jan. 3, 2005, by Frodis et al., and entitled “Method and Apparatusfor Maintaining Parallelism of Layers and/or Achieving Desired Thicknessof Layers During the Electrochemical Fabrication of Structures”. Thisreferenced application is incorporated herein by reference as if setforth in full herein.

FIG. 18A provides a cut perspective view of a fixture 952 that includesa can-like structure 962 and a masking ring structure 972. The can-likestructure may include a lid 958, a ledge 966 for supporting the maskingring, and one or more handling grooves 970. The fixture and moreparticularly the masking ring is intended to mask endpointing pads onthe wafer 950 (i.e. a substrate and deposited layers of structural andsacrificial material) during vacuum deposition. FIG. 18B provides aperspective view of the masking ring 972 with pad masking surfaces 956and cutouts 964 for exposing alignment targets. FIG. 18C provides aperspective view of the can 962 and masking ring 972 without the wafer950 in place. In this case, three pad-masking surfaces 956 are provided,one for each of three endpointing pads. The overall structure of thefixture is that of a ring with the pad-masking surfaces 956 protrudinginward from the ring surface by an amount sufficient to allow depositiononto the wafer in the area of the ring other than where the pad-maskingsurfaces are in contact or near-contact. The ring may include featuressuch as cutouts 964 to enhance deposition in certain features (e.g.alignment targets) where it might otherwise be less reliable. Thefixture 952 may be used underneath a wafer 950 which is placed so thatthe surface 954 to be deposited onto is face-down (as shown in FIG.18A); alternatively, the ring may be placed on top of a wafer whosesurface to be deposited onto is face-up. Of course other orientationsduring deposition are also possible. Alignment between the areas of thewafer to be masked and the masking surfaces on the fixture may beachieved visually, through the use of pins or other mechanical elements,a flat or flats located on the side of the wafer and on the inside ofthe fixture so that only appropriate loading is possible. In someembodiments, a mechanism such as a clamp, screws, etc. (not shown) maybe provided to hold the fixture in precise relationship to the waferonce aligned. The fixture is preferably made from a metal or othermaterial that can tolerate the temperatures associated with thedeposition process, and which does not outgas or otherwise contaminatethe deposition process.

When depositing material in a vacuum chamber, it may also be desirableto avoid deposition on surfaces of the wafer other than the surface ontowhich layers are formed. For example, deposition onto the backside of awafer may interfere, if it is not sufficiently uniform or too coarse intexture, with reliable holding of the wafer with a vacuum chuck. In suchcases (as seen in FIG. 18A), the fixture may include a backside lid 958.In other words the wafer may be placed within a can-like fixture ofsuitable material which masks off the surfaces which are not to bedeposited onto. The can may include the masking ring described above asan integral part thereof; the ring may be separate from the can and maybe supported by a ledge or other structure within the can.

When depositing material in a vacuum chamber (e.g., sputtering NiTi), itmay in some cases be necessary to stop the deposition process to allowthe wafer to cool down. In some embodiments, the wafer may be placed inintimate contact with a chuck made of a material (e.g., Cu) that hashigh thermal conductivity and preferably with a large thermal mass so asto draw heat away from the wafer. The chuck may also be provided withcooling channels (not shown) through which a cooling fluid is passed.

Seam Elimination

When depositing materials that create grain structures (e.g. NiTi) usingcertain physical vapor deposition (e.g., sputtering) or chemical vapordeposition processes over topography associated with apreviously-deposited patterned first (e.g., sacrificial) material, a‘seam’ may form, and be seen, in the deposited material. The seamtypically is offset inwards from, and follows, the edges of features.Since on each layer deposited material is sputtered into a cavity formedby previously-deposited sacrificial material, seams may be produced atthe discontinuity between grains growing horizontally out from thesidewalls of the sacrificial material and those growing vertically fromthe surface of the previous layer. Since, in the case of NiTi, thesputtering produces an amorphous structure, it must be annealed toobtain a polycrystalline structure. In such cases extended annealing maybe used to minimize such seams. In some embodiments, changing the angleof the sidewall of the first (e.g., sacrificial) material that isdeposited prior to the structural material deposition can reduce theseam. The angle may be made significantly steeper or shallower than 90°to achieve the desired effect. In some embodiments, the deposition ofthe structural material (e.g. NiTi) may be adjusted to maximize theanisotropy of the process, typically to enhance the deposition rate onhorizontal (i.e., parallel to the layers) surfaces compared with that onmore vertical surfaces. In some embodiments, removing a certainthickness of material from the finished structure, particularly if theseam is not too distant from the edge of features, may be useful.Electropolishing, chemical etching, and other material removal methodsmay be used for this purpose.

Another effect associated with the topography of thepreviously-deposited sacrificial material is ‘shadowing’, caused by theprotruding regions of the first material obscuring at least in part theedges of the apertures formed by the first material and thus affectingthe thickness of the NiTi deposited therein. Shadowing effects may bemitigated by increasing the spacing between wafer and target in thesputtering chamber and/or increasing the diameter of the target withrespect to the wafer. An alternative method to minimize shadowingeffects is to periodically or continuously change the angle of the waferwith respect to the sputtering target. One way in which this may beaccomplished is to mount the wafer (and/or target) on one or morerotating stages (e.g., a 2-axis tip/tilt stage) within the sputteringchamber and to move it during the deposition process (if desired, theprocess can be interrupted, the wafer re-positioned, and the depositionresumed).

Seams, shadowing defects and other potential effects of depositing overprevious topography (due to the existence of patterned sacrificialmaterial) in general are exacerbated by the aspect ratio of thesacrificial material features. Thus choosing a layer thickness which isno more than, and may be even a fraction of, the smallest significantfeature on the layer, is a useful technique. In some embodiments, sincethere may be non-uniformity of the sacrificial material as-deposited,planarizing the sacrificial material (e.g., using diamond machining orlapping) before depositing the structural material may be beneficial. Insome embodiments, prior to planarizing the sacrificial material atemporary filler material (e.g., wax such as Crystalbond made by AremcoProducts, Valley Cottage, N.Y.) may be deposited within any voids oraperture in the sacrificial material to stabilize them. The temporaryfiller material may be removed subsequent to the planarization.

Multi-Layer Thin Film NiTi

The use of a multilayer processes, such as the EFAB® microfabricationtechnology, to fabricate devices or structures from ‘smart’ materialssuch as shape memory alloys (e.g. NiTi) that may be 100 s of μm toseveral mm in height is an alternative to producing such devices usingconventional machining (bending, laser cutting, etc.) of bulk shapes(tubing, wire, strip, etc.). One benefit to the multilayer additivefabrication approach is the ability to build sizeable structures fromsputtered structural materials. Sputtered materials (e.g. NiTi) can behigher in purity than bulk materials, and EFAB processing may be lesslikely to introduce impurities than some conventional processing of bulkmaterials. It is known, for example, that drawing of NiTi tubing mayintroduce impurities that can cause pitting or other corrosion of a NiTidevice formed there from.

Another benefit of a multilayer additive fabrication approach is thereduction in necessary post-processing such as shape-setting.Conventionally-fabricated NiTi devices (e.g., formed from wire or tube)typically need to be formed into the desired shape—oftenindividually—and then heat set; this is commonly an iterative process.Devices produced from multiple layers can certainly be deformed andheat-set as well; for example, layers may be rotated out of theiroriginal planes, which can be advantageous in certain designs (e.g.,fabrication of rotary joints such as hinges, bushings, and bearings withrotation around axes not parallel to the build axis). However, theability to produce a complex, 3-D, freeform device can often obviate theneed for further heat-setting. Such a device can then be deformed fromits as-fabricated position and return to it either spontaneously (ifsuperelastic at the operating temperature) once the stress is removed,or after heating if serving as a shape memory actuator.

A further benefit of a multi-layer approach (in which NiTi is depositedover a patterned sacrificial material and then planarized back in aprocess similar to Damascene processing) is that this approach topatterning NiTi, when compared with commonly-used laser cutting, doesnot produce thermal damage (including effects on shape-memory behaviorsuch as shifting the transformation temperature), burrs, melting,cracks, dross on the surface, etc., and produces very clean edges. Whencompared with (normally isotropic) etching techniques to pattern NiTi,the multi-layer approach provides better resolution, greater accuracy,and sidewalls that are flatter and much closer to perpendicular to themajor surfaces of the device (i.e. perpendicular to the surface of thelayers). Overall, these advantages can make the approach of patterning asacrificial material, followed by blanket depositing NiTi, followed byplanarization, a preferred approach even if building devices with only asingle layer (e.g., a stent fabricated as a flat sheet and then rolledup).

The ability to create multi-layer structures from NiTi also opens upentirely new capabilities in device fabrication. Some of these relate tothe ability to alter the properties of the NiTi on a layer-by-layerbasis. For example, each layer can be deposited with a differentcomposition, producing compositionally-modulated structures. Since thetransformation temperature of NiTi is dependent on the ratio of Ni to Ti(decreasing rapidly with increasing Ni content) and impurityconcentrations, structures with modulated (e.g., graded) transformationtemperature can be produced by carefully controlling the materialspresent in the sputtering chamber and/or the sputtering conditions.

Transformation temperature can also be modified by heat treatment, oraging. Normally such aging increases the transformation temperature. Itis possible to age a multi-layer structure after each layer isdeposited. In some embodiments the aging is done by putting thestructure into an oven or furnace. In this case, previously-depositedlayers will be heated similarly to the last-deposited layer. Since bothtime and temperature effect transformation temperature, thenearlier-deposited layers will in general accumulate more time at hightemperature, and thus tend to have a higher transformation temperaturethan later-deposited layers, providing a gradient that can be useful. Insome embodiments, methods of heating (e.g., using a laser), especiallyif the heating is done quickly, pulsed, etc.) can preferentially heatthe most recently-deposited layer(s), creating transformationtemperature variation along the Z (layer-stacking) axis that may becontrolled more arbitrarily. In general when heating structures prior tothe deposition of all layers and the subsequent release of sacrificialmaterial, if may be desirable to build the structures on a metallicsubstrate (vs. a ceramic one) to minimize the mismatch of coefficient ofthermal expansion.

Transformation temperature can also be modified by cold-working thematerial; typically the more cold-working, the lower the transformationtemperature. Multi-layer devices can be independently cold-worked on alayer-by-layer basis by, for example, shot peening or cold rolling ofthe NiTi after deposition (in some embodiments, after planarization ofthe layer). Distortions in the width of features caused by suchprocessing can be characterized and then compensated for in the designof the device.

In some embodiments, providing different transformation temperatures fordifferent layers (hereinafter, “heterogeneous transformation”) may beused to provide a gradual increase in force and/or displacement in ashape memory actuator. Normally, heating a shape memory actuator to itstransformation temperature will cause the device to rather suddenlychange its shape; to the extent that this change in shape is resisted, aforce will thus be developed. With a heterogeneous transformationdevice, some layers will change shape and/or exert forces at differenttimes than others do as the device is heated or cooled. Thus, forexample, a heterogeneous transformation bar of NiTi may bend as it isheated just a small amount at first due to one or more of its layersreaching its transformation temperature; as the bar is further heatedother layers will reach their transformation temperature and furtherbending will occur. In some embodiments, the thickness of layers, aswell as their transformation temperature, may be used to control thedisplacements and forces produced by the device, since thinner layerswill in general produce less relative force than thicker ones.Controlling both thickness and transformation temperature on alayer-by-layer basis thus enables a great deal of control over thebehavior of a multi-layer device.

In one embodiment of a heterogeneous transformation device, the shapesobtained upon changing temperature can be different than those producedby shape setting. This may facilitate or enable shape-setting of deviceswhich might otherwise be difficult or uneconomical. For example,consider a heterogeneous transformation wire having a gradient oftransformation temperature across its diameter (i.e., it is comprised oflayers with different transformation temperatures, such at a given layerhas a transformation temperature higher than the layer below (or above)it, and a transformation temperature lower than the layer below ((orabove) it. If this wire is shape-set in a fixture that stretches it andthen raised to the transformation temperature of the layer with thelowest transformation temperature, then this layer will try to elongate,applying a force to the wire that tends to bend it away from that layer.As the temperature of the wire is raised further, additional layers willelongate until the force created by the wire in bending, and the amountof bending, is maximum. Increasing the temperature further will causeelongation of layers on the opposite side of the neutral axis, thusreducing the amount of bending and the bending force. Assuming alllayers are equal in thickness, when the temperature has risen to themaximum transformation temperature in the wire, the bending forces willbe balanced but the wire will be longer overall, possibly buckling.Thus, mere tensioning of the wire during shape setting is sufficient toprogram the wire to exhibit complex, bi-directional shape memorybehavior including increasing bending, decreasing bending, andelongation all based on temperature change. Since it is possible toshape-set a large numbers of wires at the same time if only tensioningthe wires is required, using a heterogeneous transformation device mayfacilitate scaling to higher volume production.

In another embodiment, the forces produced by different layers passingthrough their transformation temperatures at different times can bebalanced, so as to create a very gradual increase in force. For example,consider a heterogeneous transformation wire that is heat set in itsfree state and has a gradient of transformation temperature from itsbottom layer to its central (neutral axis) layer, and the oppositegradient from its central layer to its top layer. If the wire isstretched between two fixed objects, a certain tension will be appliedto the objects. If the wire is then heated (e.g., by Joule/resistiveheat), those layers with the lowest transformation temperature willbegin to contract, increasing the tension, but in a balanced way, due tothe symmetry of the transformation temperature distribution around theneutral axis. As the temperature rises, the transformation temperatureof other layers will be reached and they too will contribute to thetension. At some temperature, all layers will be at or above theirtransformation temperature.

In some embodiments, heterogeneous transformation shape memory actuatorscan be made to exhibit multi-stage shape change by virtue of theirmultiple transformation temperatures. For example, at temperature T1,one portion of a heterogeneous transformation shape memory actuator,formed from one or more layers, may change its shape and perform someuseful function, while the rest of the device remains in its originalshape. As the temperature is changed to temperature T2, another portionof the device may change its shape, and so on. Such multi-stage shapechanges can provide complex, pre-programmed/orchestrated, time-sequencedmotions involving multiple layers, enabling multi-step actuation,assembly, or self-assembly, and other functions simply by changing thetemperature of the device. Moving structures need not be composedstrictly of layers which serve to move them, but may include otherlayers as well.

FIGS. 19A-19D illustrate an example device that self-assembles as aresult of undergoing temperature changes. FIG. 19A shows the componentsof the device. A plate 1002 that bends in the vertical plane when heatedis anchored at its left end 1004, while a hole 1006 is provided towardits right end. A bar 1012 that bends in the horizontal plane when heatedis anchored at its right end 1014, while a pin 1016 is provided at thebottom near its left end. All the components shown are assumed to belongto a single device, and the transformation temperature of plate 1002 isassumed to be lower than that of the bar 1012. In FIG. 19B, thetemperature has been raised to the transformation temperature of theplate and the plate has bent downwards. In FIG. 19C, the temperature hasbeen raised to the transformation temperature of the bar and the bar hasbent inwards, such that the pin slides over the plate and enters thehole. In FIG. 19D, the device has been returned to its initialtemperature, but the components do not return to their initial position:the pin and hole have provided a self-locking mechanism that introducesa non-reversibility, or hysteresis, into the device. Of course,reversible self-assembling (and thus, disassembling) devices can also beproduced.

In some embodiments of heterogeneous transformation devices, differentlayers of a device may be heat set at different temperatures, eitherwhile the temperature of a device is changing in a single heat-settingprocess, or in multiple, separate processes. In some embodiments ofheterogeneous transformation devices, some layers may be used to stressother layers into shapes that can then be programmed via heat setting.In some embodiments of heterogeneous transformation devices, some layersmay be superelastic while others, having different transformationtemperatures, may act as shape memory actuators. In some embodiments,certain layers may have a different microstructure than other layers.For example, one or more layers deposited early in the sequence ofmaking a multi-layer device may be annealed, changing their structurefrom amorphous to polycrystalline. After the annealing, additionallayers may then be added and then not annealed.

Composite NiTi Structures

In some embodiments, shape memory actuators with fast response times forhigh-frequency operation can be produced by creating high-surface areadevices which can more easily dissipate heat to the surroundings. Finsand surface textures otherwise difficult or impossible to manufacture,including those based on fractal geometries, can be formed on suchdevices produced using a multi-layer process.

In some embodiments, composite devices may be formed which include notjust one structural material (e.g. NiTi) but at least a secondstructural material as well. A second structural material can be onseparate layers or the same layers as the first structural material andmay be partially or fully encapsulated by the first structural material.The second structural material may be localized in one contiguous areaor separated into multiple, isolated regions. If encapsulated or mostlyencapsulated, the second material may be particulate in nature, and mayeither be loose or compacted. In some embodiments, the second materialis a material with a much higher thermal conductivity than that of thefirst structural material. If completely encapsulated, the secondstructural material may actually be the sacrificial material whoseexposed regions will eventually be removed. For example, copper has athermal conductivity of 385 Wm-K, which is far higher than that of NiTi.Thus a shape memory actuator, in which the heated shape memory element(e.g. NiTi) can dissipate its heat through a second, high thermalconductivity material such as Cu, can be cycled at a higher frequency.Some second structural materials (e.g. Cu) may have higher electricalconductivity than the first structural material (e.g. NiTi). In suchcases, if the device is heated electrically, the parallel current paththrough the second material can undesirably increase power consumptionand decrease efficiency. Providing an electrically insulating, but stillthermally conductive (preferably thin) barrier between the firststructural material (i.e. the shape memory material) and the secondstructural material), and applying electrical current to the shapememory material, can mitigate this problem. In some embodiments, thesecond structural material is molten at the operating temperature of thedevice, such that it contributes increased thermal conductivity butminimally affects mechanical behavior such as stiffness.

By quickly absorbing heat, a second structural material can exhibit aphase change (melting or vaporizing) and provide faster response shapememory actuators. As the device is heated to produce a shape change, thephase-change temperature of the second structural material may bereached, suddenly extracting a large amount of heat from the firststructural material causing its temperature to drop quickly. This helpsto return the device to its unchanged shape before it would otherwisehave a chance to cool by convection, conduction, or radiation if thesewere the only mechanisms available to extract the heat. In someembodiments, it is desirable that the transformation temperature of thefirst structural material (i.e. the shape memory material, e.g. NiTi) besomewhat lower than the temperature at which a phase change of thesecond structural material occurs. In this way, as the device is heated,the first structural material will exhibit its shape change, and byraising the temperature slightly further, the phase change incurred bythe second structural material will abruptly extract heat from the firststructural material. In other embodiments, the transformationtemperature of the first structural material may be higher than thephase-change temperature of the second structural material. Depending onthe extent to which the device is adiabatic, device geometry, andparameters such as the heat capacities and thermal conductivities of thefirst structural material and second structural material, it is possibleto create mechanically oscillating devices using a shape memory firststructural material and a second material that experiences a phasechange.

In some embodiments, hollow shape memory actuators (e.g. based on NiTi)can be made such that a coolant (typically gas or liquid) can flowthrough the device to reduce its recovery time and allow higherfrequency actuation. In some embodiments, the channels through which thecoolant flows incorporate textures, fins, or other structures toincrease surface area and heat transfer to the coolant. Preferably thecoolant does not flow when the temperature of the device is rising tothe temperature at which its shape changes, and is allowed to flowsubstantially only after the shape change has occurred, so as to returnthe device more quickly to its ‘cold’ shape. In some embodiments, flowof coolant may be controlled by deformation of device itself. The devicemay be designed such that a change in its shape controls the flow ofcoolant (e.g., opening a valve, changing the cross-sectional area of theflow channels, etc.). The device would be heated to actuate it, and thechange in shape would then increase the flow of coolant; normally atapproximately this time, the source of heat (e.g., electrical Jouleheating of the device) would also be shut off.) After the device returnsto its low-temperature shape, the flow would be reduced. Such a devicewill have a natural frequency which is considerably higher than themaximum cycling frequency of a device that does not use flowablecoolant. If heat is applied at this frequency, the will oscillate. Insome embodiments, the device may be hollow and contains a phase-changefluid which transfers heat from one portion of the device to another,i.e., the device is in part a heat pipe. The motion of heat within thedevice can be used to increase actuation frequency, produce oscillation,etc.

In some embodiments, the composite structure comprises both a shapememory material (e.g. NiTi) and a material with a significantlydifferent coefficient of thermal expansion. For example, for the NiTialloy Nitinol (about 56 wt. % Ni), the CTE ranges from 6.6 parts permillion (ppm)/° C. (Martensite) to 11 ppm/° C. (Austenite), while theCTE of pure silver is 20 ppm/° C. In some embodiments, a bidirectionalactuator can be produced by combining shape changes associated withdifferences in thermal expansion with those associated with shapememory.

FIG. 20 provides an example of a typical bimorph device with a high CTEmaterial 1052 on the top and a relatively low CTE material 1054 on thebottom. At a temperature of T1, the device is flat, but as thetemperature is raised to T2, it bends downwards.

FIG. 21 provides another example of a bimorph in which the top material1062 is a high CTE material such as Ag, and the bottom material 1064 isa shape memory material such as NiTi. At T1, the device is flat. As thetemperature is raised to T2, the device bends downwards due to thedifference in thermal expansion of the two materials. But when thetemperature is raised further to T3, the shape memory behavior of thebottom material 1064 manifests itself, with the shape memory materialtrying to return to a configuration at which it was shape-set (here,assumed to be flat). This competes with the curvature effects associatedwith the mismatch of CTE and reduces the curvature of the device,potentially even returning it to its unbent shape as shown or bending itin the opposite direction. The device need not limit the materials tosingle layers, and the high CTE material 1062 may be encapsulated withinthe shape memory material 1064 or vice-a-versa, as long as most of eachof the two materials are offset from the neutral axis of the structure.

In some embodiments, multi-layer devices can be produced which includeregions of radiopaque materials such as gold (Au), tantalum (Ta), orplatinum (Pt) which serve as markers during X-ray guided medicalprocedures. To minimize possible galvanic corrosion and enable the useof materials which are not normally sufficiently biocompatible (such aslead (Pb)), the radiopaque material in some embodiments is a secondstructural material that is embedded/encapsulated entirely within afirst structural material that is biocompatible (e.g. NiTi) thuspreventing any exposure to body fluids and tissue.

Electropolishing

In some embodiments, NiTi devices produced according to the inventionmay be electropolished. Electropolishing may be performed on alayer-by-layer basis, after each layer is planarized, or on the entiredevice after full or partial release of sacrificial material.Electropolishing (or in some cases, polishing, chemical etching, andother processes) may be used to remove sub-surface damage associatedwith planarization processes (e.g. associated with lapping), removeinclusions of foreign material from the device (e.g., constituents ofslurries used for planarization), remove edge smearing defectsassociated with planarization, reduce surface roughness, round cornersand edges to reduce potential tissue trauma, remove burrs due tohandling, passivate the surface to make the device more biocompatible,etc. When electropolishing is performed on a layer-by-layer basis, it isalso at a wafer scale (i.e. with potentially many identical or differentdevices being formed in a batch process on the wafer), and thesacrificial material electrically connects all the exposed features ofstructural material in the layer being processed. In some embodimentschemical etching may be used in place of electropolishing. Whenelectropolishing or chemical etching removes surface damage associatedwith planarization operations that set layer boundary levels, theetching or polishing itself may be considered part of the planarizationprocess (i.e. the boundary level setting process) even if the etching orpolishing is material selective.

In some embodiments, electropolishing at a wafer scale (or device/diescale, if preferable) can also be performed after release or afterpartial release of sacrificial material. FIGS. 22A-22D depict, incross-section, an arrangement/process which allows wafer-scaleelectropolishing of a fabricated device 1102 located on a substrate1100. The arrangement shown provides at least one pre-aligned,co-fabricated electrode 1104 with the intent of eliminating orminimizing the need for additional electrodes. Pre-aligned,co-fabricated electrodes may be used in electropolishing the exteriorsurfaces of the devices, interior surfaces, or any other surfaces (e.g.,the sides of struts in a stent). In FIGS. 22A-22D, the intent is toprovide wafer-scale polishing of the inside of a tubular device (e.g., astent), by way of example. FIG. 22 shows side cut view of the deviceafter layer formation, prior to release of sacrificial material 1112,while FIG. 22 shows the device after a partial release of sacrificialmaterial 1112. The device is built slightly above a device support 1106(typically just one layer thick) and after partial release, sacrificialmaterial 1112 remains in the gap between device and support as shown.Within the device is an electrode 1104 which similarly is connected to asupport 1116 at each end (though one end may be sufficient) throughincompletely-released sacrificial material remaining in a narrow gapbetween the electrode and the support. The device support 1106 iselectrically continuous with a device pad 1108 for electrical contact,and the electrode support is continuous with an electrode pad 1118. Bymeans of the yet-unreleased sacrificial material, electrical contact isthus achieved to both device and electrode. In practice, all device padsand all electrode pads, respectively, may be bussed together tofacilitate wafer-scale electropolishing.

In FIG. 22, a power supply 1120 has been connected to the device pad1108 and electrode pads 1118 via wires 1122 and 1124 and the waferplaced in a suitable electropolishing bath 1130, as is known to the art.With electric current applied, material is removed from the device (anincrease in the inside diameter of the device is shown in the figure,not to scale). In FIG. 22, the release of sacrificial material 1112 hasbeen completed and the device has been removed from the wafer and theelectrode, designed for easy removal, is shown as being withdrawn fromthe central cavity of the device. The device may be furtherelectropolished using more conventional methods, especially, forexample, to polish its outer surfaces.

In an alternative embodiment to that shown in FIGS. 22A-22D, theelectrode is supported at only one end, directly by the electrodesupport, with no intervening sacrificial material. In this case, afterfinal release, the device is mechanically retained on the electrode (amechanical stop may be provided to prevent it from sliding offprematurely) until the electrode is bent up, allowing the device to beremoved. Alternatively, the electrode, and thus the device, may beremoved by breaking it, in which case it may be supported at both ends.

In lieu of using a staged release approach and allowing unreleasedsacrificial material to temporarily attach the device to the wafer andprovide electrical contact, in some alternative embodiments, tabs orsimilar elements formed from structural material which ultimately makecontact with device and electrode pads may be provided. In such cases,the wafer may be fully released before electropolishing and after suchprocessing, the tabs may be broken off to release the device. In lieu oftabs, straps which surround at least a part of the device (andoptionally, the electrode) and which make a low-resistant direct contactwith the device (after the device has shifted slightly after release)may be used; low-resistance contact through the conductiveelectropolishing bath may also be used.

Immersion in Acid to Passivate

In some embodiments (e.g. when devices are to be used in medicalapplications) it may be desirable to passivate the surfaces of thedevice to increase its biocompatibility or corrosion resistance. Devicesthat are produced from a plurality of layers may have complexgeometries, including internal features and nested elements that do noteasily lend themselves to passivation using electropolishing techniquesdue to portions of the device electrically shielding other portions. Insuch cases, it may be preferable to passivate the device to increase itsbiocompatibility and/or corrosion resistance by chemical means. Suchpassivating may be achieved by immersing devices, either individually,or in batches (e.g. while still retained on the wafer (e.g., afterrelease)) in a suitable passivating bath such as nitric acid or citricacid.

Co-Fabrication of Mandrels for Heat-Setting

In some embodiments it is desirable to change the as-fabricated shape ofa device to another shape, and set this new shape as the shape that thedevice will return to after stressing and/or heating. Normally a toolsuch as a mandrel is used for setting such shapes in shape memory alloystructures (e.g. NiTi structures), with the setting process done at anelevated temperature. Mutual alignment of devices or portions of devicesto such mandrels can be cumbersome and costly, and tends to be done onan individual basis or for just several devices at a time. Thedifficulty is compounded if the devices are of a small size and evenmore so if the device have microscale features.

FIGS. 23A-23E illustrate an embodiment where mandrels for shape-settingare co-fabricated along with devices. In FIG. 23 a series of devices1202 are shown on a substrate 1200 (e.g., a wafer) in cross-section, asfabricated, prior to release of sacrificial material 1204. Along withthe devices are co-fabricated robust upper mandrels 1206 and lowermandrels 1208, as well as flexures 1210 (best seen in FIG. 23) here inthe form of helical springs. In lieu of flexures, slides or otherelements can be used to help stabilize the upper mandrel in the planeparallel to the layers, while allowing motion in the desired directionthat deforms the devices. Structures other than the devices 1202 neednot necessarily be fabricated from a shape memory material (e.g. NiTi).The non-device structures (and even portions of the devices themselvesmay be formed from different structural materials) and may exist ondifferent layers from those that contain the shape memory material ormaterials or they may co-exist on the same layers along with asacrificial material. As upper mandrels exist on separate layers fromthose that contain the devices, they may easily be made from a differentstructural material. In some embodiments, the upper mandrel may not beco-fabricated with the devices. In some embodiments, only one type ofmandrel is required; for example, in the figure, it may be possible,depending on the desired shape, to eliminate the lower mandrels. FIG.22B depicts the state of the process after the build has been partiallyreleased, though thin regions 1214 and 1216 of sacrificial materialremain under the devices and the bases of the flexures, respectively, toanchor these temporarily to the substrate. In some embodiments, releasemay be facilitated by release holes 1218 in the upper mandrel. Inalternative embodiments, individual upper mandrels for each device maybe provided, allowing etchant to access the sacrificial material viagaps that separate the individual mandrels.

In FIG. 23, the state of the process is shown after the upper mandrel1206 has been pushed downward to deflect part of each device 1202 aroundthe lower mandrels 1208 while compressing the flexures 1210. Heat isapplied while the upper mandrel is maintained in this position, settingthe devices. If needed, the devices may be deflected and heat setgradually, approaching the final desired shape iteratively.

In FIG. 23, the upper mandrel 1206 has been allowed to rise up, but thedevices 1202, now heat set, remain in their final shapes.

Finally, in FIG. 23, the remainder of the sacrificial material isremoved to complete release of the individual devices 1202. Removal ofthe sacrificial material underneath the flexure bases allows the uppermandrel to be lifted away to expose the devices (assuming there is noother way to remove them), while removal of sacrificial material fromunder the devices frees them from the substrate. If it is not necessaryto remove the upper mandrel to remove the devices, then the flexurebases may be directly attached to the substrate such that the uppermandrel remains permanently attached. A process similar to that of FIGS.23-23E may also be used to produce permanent plastic deformation ofnon-shape memory materials: in effect, providing a wafer-scale stampingoperation for small devices.

Further Comments and Conclusions

Structural or sacrificial dielectric materials may be incorporated intoembodiments of the present invention in a variety of different ways.Such materials may form a third material or higher deposited on selectedlayers or may form one of the first two materials deposited on somelayers. Additional teachings concerning the formation of structures ondielectric substrates and/or the formation of structures thatincorporate dielectric materials into the formation process andpossibility into the final structures as formed are set forth in anumber of patent applications filed Dec. 31, 2003. The first of thesefilings is U.S. Patent Application No. 60/534,184 which is entitled“Electrochemical Fabrication Methods Incorporating Dielectric Materialsand/or Using Dielectric Substrates”. The second of these filings is U.S.Patent Application No. 60/533,932, which is entitled “ElectrochemicalFabrication Methods Using Dielectric Substrates”. The third of thesefilings is U.S. Patent Application No. 60/534,157, which is entitled“Electrochemical Fabrication Methods Incorporating DielectricMaterials”. The fourth of these filings is U.S. Patent Application No.60/533,891, which is entitled “Methods for Electrochemically FabricatingStructures Incorporating Dielectric Sheets and/or Seed layers That ArePartially Removed Via Planarization”. A fifth such filing is U.S. PatentApplication No. 60/533,895, which is entitled “ElectrochemicalFabrication Method for Producing Multi-layer Three-DimensionalStructures on a Porous Dielectric”. Additional patent filings thatprovide teachings concerning incorporation of dielectrics into the EFABprocess include U.S. patent application Ser. No. 11/139,262, filed May26, 2005 by Lockard, et al., and which is entitled “Methods forElectrochemically Fabricating Structures Using Adhered Masks,Incorporating Dielectric Sheets, and/or Seed Layers that are PartiallyRemoved Via Planarization”; and U.S. patent application Ser. No.11/029,216, filed Jan. 3, 2005 by Cohen, et al., and which is entitled“Electrochemical Fabrication Methods Incorporating Dielectric Materialsand/or Using Dielectric Substrates”. These patent filings are eachhereby incorporated herein by reference as if set forth in full herein.

Though the embodiments explicitly set forth herein have consideredmulti-material layers to be formed one after another. In someembodiments, it is possible to form structures on a layer-by-layer basisbut to deviate from a strict planar layer on planar layer build upprocess in favor of a process that interlaces material between thelayers. Such alternative build processes are disclosed in U.S.application Ser. No. 10/434,519, filed on May 7, 2003, entitled Methodsof and Apparatus for Electrochemically Fabricating Structures ViaInterlaced Layers or Via Selective Etching and Filling of Voids. Thetechniques disclosed in this referenced application may be combined withthe techniques and alternatives set forth explicitly herein to deriveadditional alternative embodiments. In particular, the structuralfeatures are still defined on a planar-layer-by-planar-layer basis butmaterial associated with some layers are formed along with material forother layers such that interlacing of deposited material occurs. Suchinterlacing may lead to reduced structural distortion during formationor improved interlayer adhesion. This patent application is hereinincorporated by reference as if set forth in full.

The patent applications and patents set forth below are herebyincorporated by reference herein as if set forth in full. The teachingsin these incorporated applications can be combined with the teachings ofthe instant application in many ways: For example, enhanced methods ofproducing structures may be derived from some combinations of teachings,enhanced structures may be obtainable, enhanced apparatus may bederived, and the like.

US Pat App No, Filing Date US App Pub No, Pub Date Inventor, Title09/493,496 - Jan. 28, 2000 Cohen, “Method For ElectrochemicalFabrication” 10/677,556 - Oct. 1, 2003 Cohen, “Monolithic StructuresIncluding Alignment and/or Retention Fixtures for Accepting Components”10/830,262 - Apr. 21, 2004 Cohen, “Methods of Reducing InterlayerDiscontinuities in Electrochemically Fabricated Three-DimensionalStructures” 10/271,574 -Oct. 15, 2002 Cohen, “Methods of and Apparatusfor Making High Aspect 2003-0127336A - July 10, 2003 RatioMicroelectromechanical Structures” 10/697,597 - Dec. 20, 2002 Lockard,“EFAB Methods and Apparatus Including Spray Metal or Powder CoatingProcesses” 10/677,498 - Oct. 1, 2003 Cohen, “Multi-cell Masks andMethods and Apparatus for Using Such Masks To Form Three-DimensionalStructures” 10/724,513 - Nov. 26, 2003 Cohen, “Non-Conformable Masks andMethods and Apparatus for Forming Three-Dimensional Structures”10/607,931 - Jun. 27, 2003 Brown, “Miniature RF and Microwave Componentsand Methods for Fabricating Such Components” 10/841,100 - May 7, 2004Cohen, “Electrochemical Fabrication Methods Including Use of SurfaceTreatments to Reduce Overplating and/or Planarization During Formationof Multi-layer Three- Dimensional Structures” 10/387,958 - Mar. 13, 2003Cohen, “Electrochemical Fabrication Method and 2003-022168A-Dec. 4, 2003Application for Producing Three-Dimensional Structures Having ImprovedSurface Finish” 10/434,494 - May 7, 2003 Zhang, “Methods and Apparatusfor Monitoring Deposition 2004-0000489A - Jan. 1, 2004 Quality DuringConformable Contact Mask Plating Operations” 10/434,289 - May 7, 2003Zhang, “Conformable Contact Masking Methods and 20040065555A - Apr. 8,2004 Apparatus Utilizing In Situ Cathodic Activation of a Substrate”10/434,294 - May 7, 2003 Zhang, “Electrochemical Fabrication MethodsWith 2004-0065550A-Apr. 8, 2004 Enhanced Post Deposition ProcessingEnhanced Post Deposition Processing” 10/434,295 - May 7, 2003 Cohen,“Method of and Apparatus for Forming Three- 2004-0004001A - Jan. 8, 2004Dimensional Structures Integral With Semiconductor Based Circuitry”10/434,315 - May 7, 2003 Bang, “Methods of and Apparatus for MoldingStructures 2003-0234179 A - Dec. 25, 2003 Using Sacrificial MetalPatterns” 10/434,103 - May 7, 2004 Cohen, “Electrochemically FabricatedHermetically Sealed 2004-0020782A - Feb. 5, 2004 Microstructures andMethods of and Apparatus for Producing Such Structures” 10/841,006 - May7, 2004 Thompson, “Electrochemically Fabricated Structures HavingDielectric or Active Bases and Methods of and Apparatus for ProducingSuch Structures” 10/434,519 - May 7, 2003 Smalley, “Methods of andApparatus for Electrochemically 2004-0007470A - Jan. 15, 2004Fabricating Structures Via Interlaced Layers or Via Selective Etchingand Filling of Voids” 10/724,515 - Nov. 26, 2003 Cohen, “Method forElectrochemically Forming Structures Including Non-Parallel Mating ofContact Masks and Substrates” 10/841,347 - May 7, 2004 Cohen,“Multi-step Release Method for Electrochemically Fabricated Structures”60/533,947 - Dec. 31, 2003 Kumar, “Probe Arrays and Method for Making”60/534,183 - Dec. 31, 2003 Cohen, “Method and Apparatus for MaintainingParallelism of Layers and/or Achieving Desired Thicknesses of LayersDuring the Electrochemical Fabrication of Structures”

Though various portions of this specification have been provided withheaders, it is not intended that the headers be used to limit theapplication of teachings found in one portion of the specification fromapplying to other portions of the specification. For example, it shouldbe understood that alternatives acknowledged in association with oneembodiment, are intended to apply to all embodiments to the extent thatthe features of the different embodiments make such applicationfunctional and do not otherwise contradict or remove all benefits of theadopted embodiment. Various other embodiments of the present inventionexist. Some of these embodiments may be based on a combination of theteachings herein with various teachings incorporated herein byreference.

In view of the teachings herein, many further embodiments, alternativesin design and uses of the embodiments of the instant invention will beapparent to those of skill in the art. As such, it is not intended thatthe invention be limited to the particular illustrative embodiments,alternatives, and uses described above but instead that it be solelylimited by the claims presented hereafter.

1. In a method of forming a multi-layer three-dimensional structure,including: (A) forming a plurality of successive layers of the structurewith each successive layer, except for a first layer, adhered to apreviously formed layer and with each successive layer comprising atleast two materials, one of which is a structural material and the otherof which is a sacrificial material, and wherein each successive layerdefines a successive cross-section of the three-dimensional structure,and wherein the forming of each of the plurality of successive layersincludes: (i) depositing a first of the at least two materials; (ii)depositing a second of the at least two materials; and (B) after theforming of the plurality of successive layers, separating at least aportion of the sacrificial material from the structural material toreveal the three-dimensional structure, wherein the improvementcomprises: depositing the first material via an electrodepositionprocess during formation of a given layer; depositing the secondmaterial via a non-electrodeposition process during formation of a givenlayer, wherein the first material is a metal and wherein the secondmaterial is an HDET metal, and wherein the first material is thesacrificial material and the second material is the structural material.2. The method of claim 1 wherein at least a portion of a surface of aprevious formed layer is treated to remove oxides over a previouslydeposited HDET metal to prepare the surface for receiving anelectrodeposition of the first material during the formation of thegiven layer.
 3. The method of claim 2 wherein the surface treatmentcomprises an anodic activation followed by a cathodic activation of theat least a portion of the surface.
 4. The method of claim 1 wherein atleast a portion of a surface of a previously formed layer undergoes atreatment to allow electrodeposition of the first material over an HDETmetal or to improve adhesion of the first material to an HDET metal. 5.The method of claim 4 wherein the treatment comprises vacuum depositionof a relatively thin coating of the first material after which arelative thick coating of the first material is deposited via theelectrodeposition process.
 6. The method of claim
 4. wherein thetreatment comprises vacuum deposition of a relatively thin coating of astructural material which may be the same as the second material ordifferent from the second material.
 7. The method of claim 4 whereinprior to the treatment, the surface undergoes a preliminary treatment toremove any oxides.
 8. In a method of forming a multi-layerthree-dimensional structure, including: (A) forming a plurality ofsuccessive layers of the structure with each successive layer, exceptfor a first layer, adhered to a previously formed layer and with eachsuccessive layer comprising at least two materials, one of which is astructural material and the other of which is a sacrificial material,and wherein each successive layer defines a successive cross-section ofthe three-dimensional structure, and wherein the forming of each of theplurality of successive layers includes: (i) depositing a first of theat least two materials; (ii) depositing a second of the at least twomaterials; and (B) after the forming of the plurality of successivelayers, separating at least a portion of the sacrificial material fromthe structural material to reveal the three-dimensional structure,wherein the improvement comprises: depositing the first material via anon-electrodeposition process during formation of a given layer;depositing the second material via an electrodeposition process duringformation of the given layer, wherein the first material is an HDETmetal and wherein the second material is a metal, and wherein the firstmaterial is the structural material and the second material sacrificialmaterial.
 9. The method of claim 8 wherein at least a portion of asurface of a previous formed layer is treated to remove oxides over apreviously deposited HDET metal to prepare the surface for receiving anelectrodeposition of the second material during the formation of thegiven layer.
 10. The method of claim 8 wherein the surface treatmentcomprises an anodic activation followed by a cathodic activation of theat least a portion of the surface.
 11. The method of claim 8 wherein atleast a portion of a surface of a previously formed layer undergoes atreatment to allow electrodeposition of the second material over an HDETmetal or to improve adhesion of the second material to an HDET metal.12. The method of claim 11 wherein the treatment comprises vacuumdeposition of a relatively thin coating of the second material afterwhich a relative thick coating of the second material is deposited viathe electrodeposition process.
 13. The method of claim 11 wherein thetreatment comprises vacuum deposition of a relatively thin coating of astructural material which may be the same as the first material ordifferent from the first material.
 14. The method of claim 11 whereinprior to the treatment, the surface undergoes a preliminary treatment toremove any oxides.
 15. In a method of forming a multi-layerthree-dimensional structure, including: (A) forming a plurality ofsuccessive layers of the structure with each successive layer, exceptfor a first layer, adhered to a previously formed layer and with eachsuccessive layer comprising at least three materials, one of which is astructural material and the other of which is a sacrificial material,and wherein each successive layer defines a successive cross-section ofthe three-dimensional structure, and wherein the forming of each of theplurality of successive layers includes: (i) depositing a first of theat least two materials; (ii) depositing a second of the at least twomaterials; and (B) after the forming of the plurality of successivelayers, separating at least a portion of the sacrificial material fromthe structural material to reveal the three-dimensional structure,wherein the improvement comprises: depositing a first materialstructural or sacrificial material during formation of a given layer;depositing a second structural or sacrificial material during formationof the given layer, depositing a third structural or sacrificialmaterial during formation of the given layer, wherein at least one ofthe first-third materials is a sacrificial material, at least one of thefirst-third materials is a structural material, at least two of thefirst-third materials are metals, and least one of the metals iselectrodeposited, and at least one structural material is an HDET metal16. The method of claim 15 wherein at least a portion of a surface of aprevious formed layer is treated to remove oxides over a previouslydeposited HDET metal to prepare the surface for receiving anelectrodeposition of at least one of the metals during the formation ofthe given layer.
 17. The method of claim 15 wherein the surfacetreatment comprises an anodic activation followed by a cathodicactivation of the at least a portion of the surface.
 18. The method ofclaim 15 wherein at least a portion of a surface of a previously formedlayer undergoes a treatment to allow electrodeposition of at least oneof the metals over an HDET metal on a previous layer or to improveadhesion of the electrodeposited metal to the HDET metal on the previouslayer.
 19. The method of claim 18 wherein the treatment comprises vacuumdeposition of a relatively thin coating of a sacrificial material afterwhich a relative thick coating of the sacrificial material is depositedvia an electrodeposition process.
 20. The method of claim 18 wherein thetreatment comprises vacuum deposition of a relatively thin coating of astructural material which may be the same as the electrodeposited metalof different from the first material.